Implement new `exec` write-hook runner that will execute arbitrary binaries

Implement new `exec` write-hook runner that will execute arbitrary binaries

Added new feature to the "code formatter" function which allows standalone
executable tools to be run against code, without going through the Python
interpreter.  Known as the ``exec`` runner, it complements the existing
``console_scripts`` runner by allowing non-Python tools such as ``ruff`` to
be used.   Pull request courtesy Mihail Milushev.

Fixes: #1275
Closes: #1276
Pull-request: https://github.com/sqlalchemy/alembic/pull/1276
Pull-request-sha: 24e576b9d8aa0d3931f2b0c0c15bb370577d7485

Change-Id: Ie28f2b7faf2fb8493c8e704f51e3e3524982e346