Report Activity config changes only if it handles the change

In S, we don't dispatch #onConfigurationChanged callback if the screen
size changes doesn't corss size buckets. However,user may still want
to know the change even if it's very small.
This CL changes to dispatch the callback if the Activity handles
the config changes.
Also clean-up the unused code.

Bug: 202468254
Test: atest AppConfigurationTests
Change-Id: Ief68922ed80a0fcfc05c7ccb5e3692334352a2c3