Network sync refactoring (part 4) (#11412)

* Remove direct dependency of `sc-network` on `sc-network-light`

* Move `WarpSyncProvider` trait and surrounding data structures into `sc-network-common`

* Move `WarpSyncProvider` trait and surrounding data structures into `sc-network-common`

* Create `sync` module in `sc-network-common`, create `ChainSync` trait there (not used yet), move a bunch of associated data structures from `sc-network-sync`

* Switch from concrete implementation to `ChainSync` trait from `sc-network-common`

* Introduce `OpaqueStateRequest`/`OpaqueStateResponse` to remove generics from `StateSync` trait

* Introduce `OpaqueBlockRequest`/`OpaqueBlockResponse`, make `scheme` module of `sc-network-sync` private

* Surface `sc-network-sync` into `sc-service` and make `sc-network` not depend on it anymore

* Remove now unnecessary dependency from `sc-network`

* Replace crate links with just text since dependencies are gone now

* Remove `warp_sync` re-export from `sc-network-common`

* Update copyright in network-related files

* Address review comments about documentation

* Apply review suggestion

* Rename `extra_requests` module to `metrics`

Co-authored-by: Bastian Köcher <info@kchr.de>