Add support for GHC-9.0.1

[anka-213]

This probably has a lot of conflicts with #53, but I just wanted something that would build on ghc-9.0.1, since this is a dependency of haskell-language-server.

(See also haskell/haskell-language-server#297)

[anka-213]

Note that this depends on mokus0/th-extras#8 to build on ghc-9.0.1, since th-extras doesn't build on ghc-9.0.1 yet either.

[felixonmars]

The test suite is still broken:

[1 of 1] Compiling Main             ( test/test.hs, dist/build/test/test-tmp/Main.dyn_o )

test/test.hs:99:1: error:
    • Could not deduce (GEq Qux) arising from a use of ‘geq’
      from the context: a ~ [a1]
        bound by a pattern with constructor:
                   L :: forall a. Qux a -> Int -> Baz [a],
                 in an equation for ‘geq’
        at test/test.hs:99:1-15
      or from: b ~ [a2]
        bound by a pattern with constructor:
                   L :: forall a. Qux a -> Int -> Baz [a],
                 in an equation for ‘geq’
        at test/test.hs:99:1-15
    • In a stmt of a 'do' block: Refl <- (geq x_a6vD) y_a6vF
      In the expression:
        do Refl <- (geq x_a6vD) y_a6vF
           guard (x_a6vE == y_a6vG)
           return Refl
      In an equation for ‘geq’:
          geq (L x_a6vD x_a6vE) (L y_a6vF y_a6vG)
            = do Refl <- (geq x_a6vD) y_a6vF
                 guard (x_a6vE == y_a6vG)
                 return Refl
   |
99 | deriveGEq ''Baz
   | ^^^^^^^^^^^^^^^