Harden startNextMatchingActivity() caller identity propagation. Currently, startNextMatchingActivity propagates the original caller's identity to the next resolved activity. This enables an "identity squashing" vulnerability where a malicious intermediary can trampoline an implicit intent from a privileged app to a victim app, bypassing permission checks (e.g. REQUEST_INSTALL_PACKAGES). This change restricts identity forwarding to prevent caller ID spoofing. The original caller's identity (launchedFromPackage/launchedFromUid) is now only propagated if: 1. The intermediary activity shares the same App ID as the original caller. 2. The intermediary activity is a privileged system component (e.g. SYSTEM_UID), preserving expected behavior for system trampolines like ChooserActivity. If these conditions are not met, the caller identity is safely reset to the intermediary's own UID and package name. Bug: 471797575 Test: atest WmTests:ActivityTaskManagerServiceTests Test: Verified via test app Flag: EXEMPT CVE_FIX Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:995f95376eb373d9e8d584883a87ebb90db609d0 Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:2b02232721942885bb45f9c72e2b70200e433c1d Merged-In: I3df4b731bfae6ce6f8896c69ecdd118819057b36 Change-Id: I3df4b731bfae6ce6f8896c69ecdd118819057b36