registration: Provide credits information to callbacks

registration: Provide credits information to callbacks

Registration callbacks now provide basic credits information (name,
path, type, authors, license-name, version, etc.) as the first argument.
The main use case right now for this is to support extension VERSION
constants for backwards-compatibility.

In addition, callbacks now run *after* attributes are exposed, so
callbacks could use data from them if they wanted to.

Bug: T151136
Change-Id: Ic5965dd4e259e1f46222ac92b8e78750e67b51d6