Buffered connection management for collator-protocol (#6022)

* Extract metrics into a separate module

* Introduce validators buffer

* Integrate buffer into the subsystem

* Only reconnect on new advertisements

* Test

* comma

* doc comment

* Make capacity buffer compile time non-zero

* Add doc comments

* nits

* remove derives

* review

* better naming

* check timeout

* Extract interval stream into lib

* Ensure collator disconnects after timeout

* spellcheck

* rename buf

* Remove double interval

* Add a log on timeout

* Cleanup buffer on timeout