Handle PendingIntents for ACSD

Finsky for some reason sends Intent.ACSD in notification trampolines
by calling PendingIntent.getBroadcast(...).send() instead of
Context.sendBroadcast(). The problem is that because it's using a PI,
the callingPid is righfully -1 (since the process could have been killed
or even restarted w/ a different pid by the time the PI is fired), so we
don't allow by the trampoline exemption for Intent.ACSD for targetSdk <
S.

In order to support that use-case, we need to look up the current
processes for the given UID, which removes the need to receive a
WindowProcessController altogether.

Bug: 183274733
Test: atest -d CtsAppTestCases:android.app.cts.CloseSystemDialogsTest
Change-Id: I0c1f21a21f1dac311cea5f6276c84e590b2cc0ef