fix: always log savepoint release

[simPod]

Q	A
Type	bug
Fixed issues	https://github.com/doctrine/dbal/pull/4846#discussion_r733214489

Summary

I've been tasked with this in https://github.com/doctrine/dbal/pull/4846#discussion_r733214489 but since that PR is huge already, I'd like to extract some parts that are not required there.

Connection::releaseSavepoint() is public so the relevant logging should be moved within it.

Also this cleans up the commit() since

this block seems to be dealing with the APIs at two different levels of abstractions which warrants some cleanup in order to keep it comprehensible