Simplify a few chain components creation APIs related to the service (#6611)

* Simplify a few chain components creation APIs related to the service

* Fix basic-authorship doc tests

* Remove DefaultQueue

* Update client/service/src/builder.rs

Co-authored-by: André Silva <[email protected]>

* Move ExecutionExtensions comment around

* Remove unused BlakeTwo256

Co-authored-by: André Silva <[email protected]>