Network sync refactoring (part 2) (#11322)

* Move `api.v1.proto` schema into new crate `sc-network-sync`

* Move `sc_network::protocol::sync::state` module into `sc_network_sync::state`

* Move `sc_network::protocol::sync::blocks` module into `sc_network_sync::blocks` and some data structures from `sc_network::protocol::message` module into `sc_network_sync::message`

* Move some data structures from `sc_network::config` and `sc_network::request_responses` into new `sc-network-common` crate

* Move `sc_network::protocol::sync::warm` and `sc_network::warp_request_handler` modules into `sc_network_sync`

* Move `client/network/sync/src/lib.rs` to `client/network/sync/src/lib_old.rs` to preserve history of changes of the file in the next commit

* Move `client/network/src/protocol/sync.rs` on top of `client/network/sync/src/lib.rs` to preserve history of changes

* Move `sc_network::protocol::sync` to `sc_network_sync` with submodules, move message data structures around accordingly

* Move `sc_network::block_request_handler` to `sc_network_sync::block_request_handler`

* Move `sc_network::state_request_handler` to `sc_network_sync::state_request_handler`

* Add re-exports for compatibility reasons

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>