make reopt compatible with recent GHCs and dependencies

[Ptival]

I've been annoyed by having reopt stuck in the past. This is my attempt at paying the tech debt.

This required a lot of things to happen:

• Update to changes to LLVM's Config from llvm-pretty,
• Updates to the added "target triple" in LLVM modules,
• Changes to LLVM's AST,
• Dealing more explicitly with the fact that old versions of mtl were exporting for/unless/when from multiple sub-modules e.g. State or Except, whereas recently they no longer do,
• Dealing with changes in GHC's complain-ness about orphan instances / type operators,
• Some changes in aeson/attoparsec-aeson,
• Needed to relax upper bounds to match dependency bounds.

I have tested cabal build all on all 9.2.8, 9.4.8, 9.6.4, 9.8.2.
I have also tried on 8.10.7, it seems to work, though I get linker errors in macaw-base so couldn't fully test.

Pinging @RyanGlScott as a general knowledgeable person, and @staslyakhov to check whether this would impact your work (hopefully not).

[RyanGlScott]

Looks reasonable at a quick glance.