Bug 1845946 - Part 3. Use NS_InitMinimalXPCOM with the GMP process. r=media-playback-reviewers,alwu

This patch brings up the basic plumbing necessary in the GMP process to
get benefits such as logging integration via the pref updates used by
about:support. Given the priority to get logging specifically working,
this patch leaves a few things unfinished for a future bug. Specifically
DLL services (for blocking antivirus on Windows) and BGHM.

Differential Revision: https://phabricator.services.mozilla.com/D185337