[llvm] [NFC][TableGen] Refactor JSON and detailed record emitter (PR #105770)

[Rahul Joshi via llvm-commits]

jurahul wrote:

> A note for the future: it would be much easier to review if formatting changes like variable renaming were in a separate commin (not necessarily in separate PR).

Thanks, and agreed. The PR evolved over time. I was actually working on splitting it up since the JSON one has many changes (const ref, var name,  no else after return etc), so I was thinking of splitting the JSON and Detailed as 2 separate PR. Let me know if that helps. (Its easy enough to do that)

https://github.com/llvm/llvm-project/pull/105770