Remove plain `startActivity` plumbing APIs am: 031a84bc72

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/IntentResolver/+/21353731

Change-Id: I8029f2296baf1427b1d3deaeb4cf20e0e821bacb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>