Separate Module AST from GhcPass

#18936 (closed) was closed out, but there was one glaring omission: HsModule.

In #17642 (closed) / !2423 (closed), HsModule was made momomorphic in GhcPs. But per the principle that the unextended AST should be "complete", I think that should be reverted, and a new Language.Haskell.Syntax.Module made.

What @int-index wrote in #17642 (closed) is also interesting (to me at least) and relevant here:

Actually, I would rather see the opposite happen. The renamer could take HsModule GhcPs as input and produce HsModule GhcRn as output.

It is fairly strange that we have

type ParsedSource      = Located (HsModule GhcPs)
type RenamedSource     = (HsGroup GhcRn, [LImportDecl GhcRn], Maybe [(LIE GhcRn, Avails)],
                          Maybe LHsDocString)
type TypecheckedSource = LHsBinds GhcTc

instead of

type ParsedSource      = Located (HsModule GhcPs)
type RenamedSource     = Located (HsModule GhcRn)
type TypecheckedSource = Located (HsModule GhcTc)

@RyanGlScott scott pointed out issues like [HsDecl p] vs HsGroup p would need to be resolved, but this doesn't daunt me. We are dealing with somewhat similar issues in !4782 (closed) right now (though I think !4782 (closed) is harder!), and so I don't doubt we could fix things here to.

(Probably the answer is the HsGroup should just be included in HsModule. HsGroup is currently not included in any other GHC-agnostic AST node.)

Finally, note per !4778 (comment 324914) this will necessitate splitting GHC.Hs.Doc and GHC.Hs.ImpExp too.