Modify source stamp format

Modify source stamp verifier to account for APK signature schemes V1,
V2, and V3. The verifier would verify the signature schemes found in the
APK.

If the APK is signed using a signature scheme that does not have a
corresponding verified source stamp signed digest, the source stamp is
considered unverified.

Bug: 158196850
Test: atest FrameworksCoreTests:SourceStampVerifierTest
Change-Id: I07e3606a346b598d192771945335770ce964726e