Add make style-todo and fourmolu on off comments

[philderbeast]

Addresses the parser errors of fourmolu so that #10491 can proceed without having to add {- FOURMOLU_DISABLE -} comments.

$ make style-todo
Cabal-described/src/Distribution/Utils/CharSet.hs:116:1-6
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error on input `insert'
Cabal-tests/tests/HackageTests.hs:304:5-9
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error on input `parse'
Cabal-tests/tests/ParserTests.hs:205:1
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error (possibly incorrect indentation or mismatched brackets)
Cabal-tests/tests/custom-setup/CabalDoctestSetup.hs:287:1
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error (possibly incorrect indentation or mismatched brackets)
Cabal-tests/tests/custom-setup/IdrisSetup.hs:95:1-5
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error on input `where'
cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs:175:1
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error (possibly incorrect indentation or mismatched brackets)
cabal-testsuite/src/Test/Cabal/Server.hs:267:34-35
  The GHC parser (in Haddock mode) failed:
  [GHC-58481] parse error on input `->'
make: *** [Makefile:55: style-todo] Error 102

---

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[9999years]

LGTM, thanks!

[philderbeast]

Label merge+no rebase is necessary when the pull request is from an organisation.

[philderbeast]

Sorry I missed squashing these down to one. I'll make sure not to apply the merge label before doing that in future.