Prepare for network protocol version upgrades (#5084)

* explicitly tag network requests with version

* fmt

* make PeerSet more aware of versioning

* some generalization of the network bridge to support upgrades

* walk back some renaming

* walk back some version stuff

* extract version from fallback

* remove V1 from NetworkBridgeUpdate

* add accidentally-removed timer

* implement focusing for versioned messages

* fmt

* fix up network bridge & tests

* remove inaccurate version check in bridge

* remove some TODO [now]s

* fix fallout in statement distribution

* fmt

* fallout in gossip-support

* fix fallout in collator-protocol

* fix fallout in bitfield-distribution

* fix fallout in approval-distribution

* fmt

* use never!

* fmt

polkadot/Cargo.lock

@@ -6587,8 +6587,10 @@ dependencies = [
 name = "polkadot-network-bridge"
 version = "0.9.19"
 dependencies = [
+ "always-assert",
  "assert_matches",
  "async-trait",
+ "bytes 1.1.0",
  "futures 0.3.21",
  "futures-timer",
  "parity-scale-codec",
@@ -6984,6 +6986,7 @@ name = "polkadot-node-network-protocol"
 version = "0.9.19"
 dependencies = [
  "async-trait",
+ "derive_more",
  "fatality",
  "futures 0.3.21",
  "parity-scale-codec",