Update API for uninstalled installers.

Expose the initiating package's signing details.

Document that we return the details of the initiating package even if
it has been uninstalled, and under what circumstances we do so.

Test: atest PackageManagerTests PackageVerifierTest
Bug: 134746019
Bug: 146555198
Change-Id: I3a5799a804a955fc52269cfac7e45173f0c06e46
4 files changed