Take care of all compiler warnings for GHC-9.8

[neilmayhew]

Description

There are new warnings in ghc 9.8 for partial functions and orphan type family instances. This fixes the warnings and re-enables -Werror for all ghc versions.

Closes #3990

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[neilmayhew]

I don't really like enabling -Wno-orphans in larger modules that have a lot of other code in them, but the three affected modules are all in cardano-ledger-test so I didn't think it was worth trying to move the instances to a better place. However, I could look into this if it would be helpful.

[Lucsanszky]

LGTM! This should be good to go once it's rebased (and the new warnings are resolved). 👍

[lehins]

Beautiful!
Thank you!