[piav2] Modify logic to compute trustedSource

A caller can be trusted if it is privileged and passed
EXTRA_NOT_UNKNOWN_SOURCE or holds the INSTALL_PACKAGES permission.

This was implemented in PiaV1 in ag/27608687

Bug: 343233266
Test: CtsPackageInstallTestCases
Flag: android.content.pm.use_pia_v2
Change-Id: Ic2ac168b56083af7e21878cf031d9987d7676cc7