Add param isCheckingForFgsStart to areBackgroundActivityStartsAllowed().

If isCheckingForFgsStart is true, this checking is for FGS start, it
won't invoke the mBackgroundActivityStartCallback.

Bug: 177642703
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java
Change-Id: Ie6d58b8886e8477a9dbc524d43ccda930139a460
2 files changed