Approve multiple candidates with a single signature (#1191)

Initial implementation for the plan discussed here: https://github.com/paritytech/polkadot-sdk/issues/701
Built on top of https://github.com/paritytech/polkadot-sdk/pull/1178
v0: https://github.com/paritytech/polkadot/pull/7554,

## Overall idea

When approval-voting checks a candidate and is ready to advertise the
approval, defer it in a per-relay chain block until we either have
MAX_APPROVAL_COALESCE_COUNT candidates to sign or a candidate has stayed
MAX_APPROVALS_COALESCE_TICKS in the queue, in both cases we sign what
candidates we have available.

This should allow us to reduce the number of approvals messages we have
to create/send/verify. The parameters are configurable, so we should
find some values that balance:

- Security of the network: Delaying broadcasting of an approval
shouldn't but the finality at risk and to make sure that never happens
we won't delay sending a vote if we are past 2/3 from the no-show time.
- Scalability of the network: MAX_APPROVAL_COALESCE_COUNT = 1 &
MAX_APPROVALS_COALESCE_TICKS =0, is what we have now and we know from
the measurements we did on versi, it bottlenecks
approval-distribution/approval-voting when increase significantly the
number of validators and parachains
- Block storage: In case of disputes we have to import this votes on
chain and that increase the necessary storage with
MAX_APPROVAL_COALESCE_COUNT * CandidateHash per vote. Given that
disputes are not the normal way of the network functioning and we will
limit MAX_APPROVAL_COALESCE_COUNT in the single digits numbers, this
should be good enough. Alternatively, we could try to create a better
way to store this on-chain through indirection, if that's needed.

## Other fixes:
- Fixed the fact that we were sending random assignments to
non-validators, that was wrong because those won't do anything with it
and they won't gossip it either because they do not have a grid topology
set, so we would waste the random assignments.
- Added metrics to be able to debug potential no-shows and
mis-processing of approvals/assignments.

## TODO:
- [x] Get feedback, that this is moving in the right direction. @ordian
@sandreim @eskimor @burdges, let me know what you think.
- [x] More and more testing.
- [x]  Test in versi.
- [x] Make MAX_APPROVAL_COALESCE_COUNT &
MAX_APPROVAL_COALESCE_WAIT_MILLIS a parachain host configuration.
- [x] Make sure the backwards compatibility works correctly
- [x] Make sure this direction is compatible with other streams of work:
https://github.com/paritytech/polkadot-sdk/issues/635 &
https://github.com/paritytech/polkadot-sdk/issues/742
- [x] Final versi burn-in before merging

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

polkadot/runtime/parachains/src/configuration/migration/v10.rs

@@ -16,17 +16,121 @@
 
 //! A module that is responsible for migration of storage.
 
-use crate::configuration::{self, Config, Pallet};
+use crate::configuration::{Config, Pallet};
 use frame_support::{pallet_prelude::*, traits::Defensive, weights::Weight};
 use frame_system::pallet_prelude::BlockNumberFor;
-use primitives::{vstaging::NodeFeatures, SessionIndex};
+use primitives::{
+	vstaging::NodeFeatures, AsyncBackingParams, Balance, ExecutorParams, SessionIndex,
+	LEGACY_MIN_BACKING_VOTES, ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
+};
+use sp_runtime::Perbill;
 use sp_std::vec::Vec;
 
 use frame_support::traits::OnRuntimeUpgrade;
 
 use super::v9::V9HostConfiguration;
+// All configuration of the runtime with respect to paras.
+#[derive(Clone, Encode, PartialEq, Decode, Debug)]
+pub struct V10HostConfiguration<BlockNumber> {
+	pub max_code_size: u32,
+	pub max_head_data_size: u32,
+	pub max_upward_queue_count: u32,
+	pub max_upward_queue_size: u32,
+	pub max_upward_message_size: u32,
+	pub max_upward_message_num_per_candidate: u32,
+	pub hrmp_max_message_num_per_candidate: u32,
+	pub validation_upgrade_cooldown: BlockNumber,
+	pub validation_upgrade_delay: BlockNumber,
+	pub async_backing_params: AsyncBackingParams,
+	pub max_pov_size: u32,
+	pub max_downward_message_size: u32,
+	pub hrmp_max_parachain_outbound_channels: u32,
+	pub hrmp_sender_deposit: Balance,
+	pub hrmp_recipient_deposit: Balance,
+	pub hrmp_channel_max_capacity: u32,
+	pub hrmp_channel_max_total_size: u32,
+	pub hrmp_max_parachain_inbound_channels: u32,
+	pub hrmp_channel_max_message_size: u32,
+	pub executor_params: ExecutorParams,
+	pub code_retention_period: BlockNumber,
+	pub on_demand_cores: u32,
+	pub on_demand_retries: u32,
+	pub on_demand_queue_max_size: u32,
+	pub on_demand_target_queue_utilization: Perbill,
+	pub on_demand_fee_variability: Perbill,
+	pub on_demand_base_fee: Balance,
+	pub on_demand_ttl: BlockNumber,
+	pub group_rotation_frequency: BlockNumber,
+	pub paras_availability_period: BlockNumber,
+	pub scheduling_lookahead: u32,
+	pub max_validators_per_core: Option<u32>,
+	pub max_validators: Option<u32>,
+	pub dispute_period: SessionIndex,
+	pub dispute_post_conclusion_acceptance_period: BlockNumber,
+	pub no_show_slots: u32,
+	pub n_delay_tranches: u32,
+	pub zeroth_delay_tranche_width: u32,
+	pub needed_approvals: u32,
+	pub relay_vrf_modulo_samples: u32,
+	pub pvf_voting_ttl: SessionIndex,
+	pub minimum_validation_upgrade_delay: BlockNumber,
+	pub minimum_backing_votes: u32,
+	pub node_features: NodeFeatures,
+}
 
-type V10HostConfiguration<BlockNumber> = configuration::HostConfiguration<BlockNumber>;
+impl<BlockNumber: Default + From<u32>> Default for V10HostConfiguration<BlockNumber> {
+	fn default() -> Self {
+		Self {
+			async_backing_params: AsyncBackingParams {
+				max_candidate_depth: 0,
+				allowed_ancestry_len: 0,
+			},
+			group_rotation_frequency: 1u32.into(),
+			paras_availability_period: 1u32.into(),
+			no_show_slots: 1u32.into(),
+			validation_upgrade_cooldown: Default::default(),
+			validation_upgrade_delay: 2u32.into(),
+			code_retention_period: Default::default(),
+			max_code_size: Default::default(),
+			max_pov_size: Default::default(),
+			max_head_data_size: Default::default(),
+			on_demand_cores: Default::default(),
+			on_demand_retries: Default::default(),
+			scheduling_lookahead: 1,
+			max_validators_per_core: Default::default(),
+			max_validators: None,
+			dispute_period: 6,
+			dispute_post_conclusion_acceptance_period: 100.into(),
+			n_delay_tranches: Default::default(),
+			zeroth_delay_tranche_width: Default::default(),
+			needed_approvals: Default::default(),
+			relay_vrf_modulo_samples: Default::default(),
+			max_upward_queue_count: Default::default(),
+			max_upward_queue_size: Default::default(),
+			max_downward_message_size: Default::default(),
+			max_upward_message_size: Default::default(),
+			max_upward_message_num_per_candidate: Default::default(),
+			hrmp_sender_deposit: Default::default(),
+			hrmp_recipient_deposit: Default::default(),
+			hrmp_channel_max_capacity: Default::default(),
+			hrmp_channel_max_total_size: Default::default(),
+			hrmp_max_parachain_inbound_channels: Default::default(),
+			hrmp_channel_max_message_size: Default::default(),
+			hrmp_max_parachain_outbound_channels: Default::default(),
+			hrmp_max_message_num_per_candidate: Default::default(),
+			pvf_voting_ttl: 2u32.into(),
+			minimum_validation_upgrade_delay: 2.into(),
+			executor_params: Default::default(),
+			on_demand_queue_max_size: ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
+			on_demand_base_fee: 10_000_000u128,
+			on_demand_fee_variability: Perbill::from_percent(3),
+			on_demand_target_queue_utilization: Perbill::from_percent(25),
+			on_demand_ttl: 5u32.into(),
+			minimum_backing_votes: LEGACY_MIN_BACKING_VOTES,
+			node_features: NodeFeatures::EMPTY,
+		}
+	}
+}
 
 mod v9 {
 	use super::*;