[Chore] Remove unneeded hack working around pattern match checker

Note: The fixup commit is for the ease of review, the first commit only removes the nested case and changes indentation. Unfortunately, this completely breaks the diff. Missing patterns are thus added as a fixup commit to make it more obvious what changed.

Description

Problem: At some point in the past, GHC couldn't handle large pattern matches. Now it can. However, we still have this hack, and hence don't statically check for the exhaustiveness of our patterns.

Solution: Remove the hack, let GHC check all the patterns.

Related issue(s)

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