Bug 1042463 - System Update prompt persists in low-battery environment

Fix prompt appearing even when battery is below allowed threshold,
introducing a new update-prompt-result event type.
Merge pull request #22495 from hobinjk/system-update-ready-prompt-battery

Bug 1042463 - System Update prompt persists in low-battery environment
Bug 1056794 - Disable test_everythingme_add_collection_save_bookmark
Bug 1048009 - Reduce overall overpaint. r=etienne
Merge pull request #23151 from bebef1987/xfail4

Bug 1056794 - Xfail test_everythingme_add_collection_save_bookmark
Merge pull request #23152 from vingtetun/reduce.overpaint.system

Bug 1048009 - Reduce overall overpaint. r=etienne
Bug 943825 - [Gaia] Mount/Unmount SD card