Namespacing for WARNING/DEPRECATED pragmas

Tracking implementation of the WARNING and DEPRECATED pragma aspects of GHC proposal #65 "Require namespacing fixity declarations for type names and WARNING/DEPRECATED pragmas".

Add syntax for {-# WARNING type D "some message" #-}, {-# WARNING data D "some message" #-} and similar syntax for the DEPRECATED pragma. Change Renamer so it will take namespace specifier into consideration.
Introduce a new warning that fires when a WARNING/DEPRECATED pragma refers to a type-level name without a specifier, and add this warning to -Wcompat.

Edited Feb 02, 2024 by Andrei Borzenkov

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