[HooksManager] Show the name of the source for each hook that is run in verbose mode

Closes https://github.com/CocoaPods/CocoaPods/issues/2639.
Closes https://github.com/CocoaPods/CocoaPods/issues/2640.

Depends upon https://github.com/CocoaPods/Core/pull/196.

Huge thanks to @alloy for the `source_location` hint! (feel free to say this all is too gross to include)

The name calculation is wrapped in a lambda so it's not called when it won't be printed out

\c @kylef would appreciate some help making sure this is a robust solution
This should include the fact we only run the hooks for plugins defined in Podfile. I think we should show an example of how you would do this.

Perhaps this is now a breaking change as it breaks previous behaviour (like [sources](https://github.com/CocoaPods/CocoaPods/blob/master/CHANGELOG.md#0340)?