refactor code generation tools , include --check command

refactor code generation tools , include --check command

in particular it looks like CI was not picking up on the
"git diff" oriented commands, which were failing to run due
to pathing issues.  As we were setting cwd for black/zimports
relative to sqlalchemy library, and tox installs it in
the venv, black/zimports would fail to run from tox, and
since these are subprocess.run we didn't pick up the
failure.

This overall locks down how zimports/black are run
so that we are definitely from the source root, by using
the location of tools/ to determine the root.

Fixes: #8892
Change-Id: I7c54b747edd5a80e0c699b8456febf66d8b62375