Fix side channel information disclosure

This method reacts differently when the given package name isn't
installed, and is installed but not belonging to the caller. This
subtle difference leaves the possibility that malicious code could
do a side channel attack.

Bug: 249058614
Test: atest CtsWindowManagerDeviceTestCases:ToastWindowTest
Test: atest CtsWindowManagerDeviceTestCases:WindowContextPolicyTests
Test: atest CtsWindowManagerDeviceTestCases:WindowUntrustedTouchTest
Test: atest CtsToastLegacyTestCases:ToastTest
Test: atest CtsToastTestCases:LegacyToastTest
Test: atest FrameworksCoreTests:ViewRootImplTest
Test: atest FrameworksUiServicesTests:NotificationManagerServiceTest
Change-Id: I37f28b6a660c4a3d2cd92b25d3f68066902c692f

Change-Id: I52372bec19355ea8855ead28fcb0ab250c527f19