Move code from `sc-network-common` back to `sc-network` (#13592)

* Move service tests to `client/network/tests`

These tests depend on `sc-network` and `sc-network-sync` so they should
live outside the crate.

* Move some configs from `sc-network-common` to `sc-network`

* Move `NetworkService` traits to `sc-network`

* Move request-responses to `sc-network`

* Remove more stuff

* Remove rest of configs from `sc-network-common` to `sc-network`

* Remove more stuff

* Fix warnings

* Update client/network/src/request_responses.rs

Co-authored-by: Dmitry Markin <dmitry@markin.tech>

* Fix cargo doc

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Co-authored-by: Dmitry Markin <dmitry@markin.tech>