Treat cross-user MediaProjection as INTERACT_ACROSS_USERS_FULL

If the package UID and calling UID don't match, we need to
use the package UID for package lookups - but only if the
caller has the appropriate permission.

Bug: 416164045
Flag: android.app.contextualsearch.flags.contextual_search_media_projection
Text: atest ContextualSearchManagerTest
Change-Id: I841eb45f96e01748eb7bbc1135f696d91e608076