repo-updater: move Blame and ResolveRevision from vcs/git to gitserver/commands package

Created by: sashaostrikov

Another refactoring PR in scope of https://github.com/sourcegraph/sourcegraph/issues/33280.

Blame and ResolveRevision commands are moved.

Blame couldn't be moved without ResolveRevision, that's why PR isn't nice in terms of size, sorry.

Closes https://github.com/sourcegraph/sourcegraph/issues/34048 and https://github.com/sourcegraph/sourcegraph/issues/35433

Test plan

Existing tests should pass