Move cert tracing to PackageParser

Tracing for cert collection in PackageManagerService was only
catching one of a couple usages. Move tracing lower in the
call stack to ensure tracing exists for all calls.

Also added a new tag to differentiate between verifying v1 & v2
signatures.

Bug: 27502465
Change-Id: Ie29f326e44f32cdbea1572714689c82f07ca12ba