Support ghc 9.12

[erikd]

Only real change is a bump to the base bounds.

To build with the current Hackage state, need the following cabal.project file:

packages:
  .

allow-newer:
  , boring:base
  , hashable:base

The base bump can be done as a Hackage metadata edit.

[erikd]

Can't add the new compiler to CI yet because it does not exist.

[gwils]

Thanks Erik, I hope you're well :)
I've made the metadata revision.

[erikd]

I am well George. Thanks for asking. And you?

[gwils]

I'm well too :)