Include the check on the mAllowStartByBindings flag in the BG-FGS start logic

The previous CL for the b/276963716 refactored the checks on the BG-FGS
start restriction. Here we're updating the check to include the flag
"mAllowStartByBindings".

There will be follow-up CLs which would eventually get rid of the
use of mAllowStartInBindService, maybe based on the targetSDK level
check.

Bug: 302248694
Test: atest android.app.cts.ActivityManagerFgsBgStartTest
Test: atest CtsShortFgsTestCases
Change-Id: I01f045bddcf78363a3295f141ff06a7f9db7e970