Previously, we implemented arg checking with marionette just carrying a free
pass, so we could let the arguments which typically come when running tests.
However, some marionette tests do like to play with arguments which we do not
want to get a free pass, such as -safe-mode. These changes allow just the
-profile argument through, as that is necessary for running tests.

Some env vars have effects similar to command line arguments which present
problems for the skeleton UI, and we want to treat these env vars similarly.

Depends on D98474

Having the window present earlier changes the ordering of these events, such
that it doesn't come through at the time that the browser_startup test needs it
to. I think this event should be correct anyway, given that we already painted
the skeleton UI?

Depends on D98476

This was causing us to have slightly wrong focusring behavior, leading to wpt
failures in focus-visible-005.html.

Depends on D98478

I don't have a crystal clear story of why these timings are different with the
skeleton UI enabled. However, it's not remarkably surprising that it changes the
order of some events during startup which come from the core Windows event loop.
I don't think it's worth diving incredibly deep to understand this - looking at
the profile we still only see one of each of these events.

Depends on D99110

I'm very confused by this? None of this is even compiled on OSX.