Asynchronous-backing compatible Aura, not plugged in (#2573)

* rough draft of potential parent search

* get things compiling

* fmt

* add new function to all RelayChainInterface implementations

* fix compilation

* set slot and timestamp based on relay parent, prepare for find-parent

* skeleton of new aura logic

* fmt

* introduce a collator module in the Aura crate

* extract different implementations into own modules

* make interface more convenient

* docs and todos for lookahead

* refactor basic collator to use new collator utility

* some more refactoring

* finish most of the control flow for new aura

* introduce backend as parameter

* fix compilation

* fix a couple more TODOs

* add an `announce_block` function to collator service

* announce with barrier

* rename block announcement validator to be more specific

* fmt

* clean up unused import errors

* update references to BlockAnnounceValidator

* rename unstable_reimpl

* add AuraUnincludedSegmentApi

* finish rename

* integrate AuraUnincludedSegmentApi

* add a new block announcement validator for backwards compatibility

* add some naive equivocation defenses

* rustfmt

* clean up remaining TODO [now]s

* fmt

* try to fix inprocess-interface

* actually fix compilation

* ignored -> rejected rephrase

* fix test compilation

* fmt

* clippy

cumulus/Cargo.lock

@@ -2584,10 +2584,12 @@ dependencies = [
  "cumulus-client-collator",
  "cumulus-client-consensus-common",
  "cumulus-client-consensus-proposer",
+ "cumulus-primitives-aura",
  "cumulus-primitives-core",
  "cumulus-primitives-parachain-inherent",
  "cumulus-relay-chain-interface",
  "futures",
+ "lru 0.10.0",
  "parity-scale-codec",
  "polkadot-node-primitives",
  "polkadot-overseer",
@@ -2595,6 +2597,7 @@ dependencies = [
  "sc-client-api",
  "sc-consensus",
  "sc-consensus-aura",
+ "sc-consensus-babe",
  "sc-consensus-slots",
  "sc-telemetry",
  "sp-api",
@@ -2630,11 +2633,14 @@ dependencies = [
  "polkadot-primitives",
  "sc-client-api",
  "sc-consensus",
+ "sc-consensus-babe",
  "schnellru",
  "sp-blockchain",
  "sp-consensus",
+ "sp-consensus-slots",
  "sp-core",
  "sp-runtime",
+ "sp-timestamp",
  "sp-tracing",
  "sp-trie",
  "substrate-prometheus-endpoint",
@@ -2933,6 +2939,19 @@ dependencies = [
  "xcm",
 ]
 
+[[package]]
+name = "cumulus-primitives-aura"
+version = "0.1.0"
+dependencies = [
+ "parity-scale-codec",
+ "polkadot-core-primitives",
+ "polkadot-primitives",
+ "sp-api",
+ "sp-consensus-aura",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "cumulus-primitives-core"
 version = "0.1.0"