Cover IntentSender by BAL hardening

When a IntentSender was sent it was exclused from BAL hardening because
an API to opt in such code was missing (but introduced in B).

Test: atest BackgroundActivityLaunchTest
Bug: 405995292
Flag: com.android.window.flags.bal_cover_intent_sender
Change-Id: Id90c1951d776071a0fbe8327ba27dfb7ecb64f17