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

Closes https://github.com/CocoaPods/CocoaPods/issues/2639.

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