Update PM#checkSignatures by uid to support pre-key rotation behavior

ag/11054988 updated PackageManager#checkSignatures to support pre-key
rotation behavior when querying by package name; this commit applies
the same logic to the checkSignatures query by uid to check against
the oldest signer in the lineage if either of the requested packages
has been through a key rotation.

Bug: 153910385
Test: atest PackageManagerTests
Test: atest PackageManagerTest
Change-Id: If35c1cdefd06048dc5addc6bbd579d2316ab323b