Update a11y when alpha changes

We were only updating accessibility in View#setAlpha,
but View#setAlphaNoInvalidation would also change alpha,
and accessibility would never find out.

Bug: 78101543
Test: TalkBack now works on nightlight conditional and
battery saver slider.

Change-Id: I1ebb62aa7f4de700b2d7fbaae8dbbd1c84fc4ece