Removes old/unused left/right button logic from bottom area.

Note: the _current/newer_ left/right button logic is _not_ removed.

This is a revert of a revert. It reverts commit 03e0b8e0.

Reason for revert: This is a revert of the revert of the original "Removes left/right buttons from bottom area." but this time without removing the ability to launch the camera on double-tap of the power button.

Bug: b/235403546
Change-Id: Ic7b42afb7240d944a366f2c1818de9bfe1f6b3f1
Test: Manually verified that the lock screen still seems to behave the same way as it did before this change. Made sure that the Wallet and Home Control buttons are still visible when configured and work in the normal way. Also made sure that a double click of the power button launches the camera. Tested three different scenarios for the camera using the double-click on the power button to launch the camera when the screen is off, when the lock-screen is showing, and when the device is unlocked and the home screen is visible. Made sure that the camera app opens smoothly and transition animations look good.