[llvm] [TableGen] Rework error reporting for duplicate Feature/Processor. (PR #102257)

[Rahul Joshi via llvm-commits]

jurahul wrote:

I assumed these are transient errors unrelated to the change, but maybe not? Though given the things touched, I am not sure how this would break things. We do now sort records with same name in different order, but also check duplicates, so if the duplicate check passes, the order should be the same as was before.

https://github.com/llvm/llvm-project/pull/102257