This simplifies cyclic dependencies for now (the registry needs to call
wl_display.sync).

Hides other wire format internals as well, since they are no longer
required to use the api.

Currently incomplete (documentation is only available on interfaces),
because TH cannot set documentation on overloaded record fields
("Ambiguous occurrence ‘destroy’").

GHC 9.2.1 also enables Template Haskell to attach Haddock documentation,
which can be used to attach documentation from the Wayland XML
specifications to their generated Haskell APIs.

Analog to how low-level messages are mapped.