Finish migration to v2 primitives (#5037)

* remove v0 primitives from polkadot-primitives

* first pass: remove v0

* fix fallout in erasure-coding

* remove v1 primitives, consolidate to v2

* the great import update

* update runtime_api_impl_v1 to v2 as well

* guide: add `Version` request for runtime API

* add version query to runtime API

* reintroduce OldV1SessionInfo in a limited way

polkadot/runtime/parachains/src/dmp/tests.rs

@@ -18,7 +18,7 @@ use super::*;
 use crate::mock::{new_test_ext, Configuration, Dmp, MockGenesisConfig, Paras, System};
 use hex_literal::hex;
 use parity_scale_codec::Encode;
-use primitives::v1::BlockNumber;
+use primitives::v2::BlockNumber;
 
 pub(crate) fn run_to_block(to: BlockNumber, new_session: Option<Vec<BlockNumber>>) {
 	while System::block_number() < to {
@@ -184,7 +184,7 @@ fn queue_downward_message_critical() {
 #[test]
 fn verify_dmq_mqc_head_is_externally_accessible() {
 	use hex_literal::hex;
-	use primitives::v1::well_known_keys;
+	use primitives::v2::well_known_keys;
 
 	let a = ParaId::from(2020);