ghc-lib-parser 9.10

[amesgen]

Depends on https://github.com/mrkkrp/path-io/pull/97

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Update to ghc-lib-parser-9.10, build with GHC 9.10.1 in CI, drop GHC 9.4, update bounds.

• See the changelog for details about the new syntactic features in GHC 9.10.
• We can remove our HasSrcSpan in favor of ghc-lib-parser's HasLoc.
• The EPA extension points in constructors do (usually) no longer contain the comments (they are now usually in the annotation part of a Located). We relied on this in p_if (as of #1092). Instead of laboriously passing the comments down from where we unwrap the LHsExpr, I added a new function getEnclosingComments to the R monad that leverages the comment stream, as that seemed much less invasive.
• See the review comments for some further minor points.