Revert "Don't allow PI-based starts and trampolines when sender"

This partially reverts commit
2927b542.

Reason for revert: Breaks legitimate uses (b/131862922)

The changes to handle TYPE_APPLICATION_STARTING are not being reverted
(RootWindowContainer and RootWindowContainerTests); they're unrelated.

Bug: 131862922
Bug: 129563343
Test: atest BackgroundActivityLaunchTest
Test: atest RootWindowContainerTests
Test: atest WmTests:ActivityStarterTests
Test: atest CtsWindowManagerDeviceTestCases:ActivityStarterTests
Test: atest CtsAppTestCases:.ServiceTest

Change-Id: Ib86b7cbff97ce3154c7e3ce7b3c7e46b33c575fe