Bug 1421766 - Make geckodriver read marionette port from MarionetteActivePort...

Bug 1421766 - Make geckodriver read marionette port from MarionetteActivePort in profile, r=webdriver-reviewers,jdescottes,whimboo

When no marionette port is explicitly specified, and the Firefox
version is >= 95, pass in a port number of 0 from geckodriver to
firefox, so that marionette binds on a free port. Then read the port
it used from the profile. This avoids the possibility of races between
geckodriver picking a free port and marionette binding to that port.

This could also be used on Android, but isn't implemented as part of
this patch.

Differential Revision: https://phabricator.services.mozilla.com/D136740