Revert "Bug 879869 - Disable startup/shutdown sound by default r=lightsofapollo"

This reverts commit 45b9a38a486c87642052e08c7213c43ac20b222c.

Conflicts:
	build/settings.py
Revert "Merge pull request #10117 from samjoch/bug-877813-SoundsControlToTurnOffBootAndShutdownSoundsIsNeededInSettings"

This reverts commit d5d898bb28b5ff931ec2bbdfe0b096b8e45329c9, reversing
changes made to b81ceb38b2eb044d8bb8a75baf7f551667e79441.

Conflicts:
	build/settings.py
Revert "Merge pull request #9284 from samjoch/bug-801895-SoundsUpdateBootSound"

This reverts commit 0ec2a2558cf41da4a2bf52bf6a550e5e2293602c, reversing
changes made to 71385ac3858d720e562f7818b01c9b62698b0478.
Revert "Merge pull request #9739 from samjoch/bug-812245-SoundShutDownAnimationNeedsASound"

This reverts commit e4bf807f22dd5c392d181a216b2e7d4ccd162308, reversing
changes made to 644c3a44023d6f8b447b8ad9d57583a1c5f6f723.
Merge pull request #10391 from samjoch/bug-883090-SoundsRemoveStartupShutdownSounds

Bug 883090 - [Sounds] Remove startup shutdown sounds and controls, r=@timdream