Allow to specify multiple relay chain RPC urls for collator node (#1880)

* Allow specification of multiple urls for relay chain rpc nodes

* Add pooled RPC client basics

* Add list of clients to pooled client

* Improve

* Forward requests to dispatcher

* Switch clients on error

* Implement rotation logic

* Improve subscription handling

* Error handling cleanup

* Remove retry from rpc-client

* Improve naming

* Improve documentation

* Improve `ClientManager` abstraction

* Adjust zombienet test

* Add more comments

* fmt

* Apply reviewers comments

* Extract reconnection to extra method

* Add comment to reconnection method

* Clean up some dependencies

* Fix build

* fmt

* Provide alias for cli argument

* Apply review comments

* Rename P* to Relay*

* Improve zombienet test

* fmt

* Fix zombienet sleep

* Simplify zombienet test

* Reduce log clutter and fix starting position

* Do not distribute duplicated imported and finalized blocks

* fmt

* Apply code review suggestions

* Move building of relay chain interface to `cumulus-client-service`

* Refactoring to not push back into channel

* FMT

client/relay-chain-interface/Cargo.toml

@@ -15,6 +15,7 @@ sp-blockchain = { git = "https://github.com/paritytech/substrate", branch = "mas
 sp-state-machine = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-client-api = { git = "https://github.com/paritytech/substrate", branch = "master" }
 
+tokio = { version = "1.21.2", features = ["sync"] }
 futures = "0.3.25"
 async-trait = "0.1.59"
 thiserror = "1.0.37"