Add autogroup on post flag

Adds flag for checking whether notification should be autogrouped on
post, rather than posting first and sending a separate ranking update
if the autogroup should happen.

Bug: 330214226
Test: mp droid
Flag: ACONFIG android.app.check_autogroup_before_post DEVELOPMENT
Change-Id: Ib908055ce4adfa00a4411f66fbc0a04e31b7444e