[llvm] Reapply "[LLVM][TableGen] Parameterize NumToSkip in DecoderEmitter" (#136017) (PR #136019)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Verified that moving to anonymous namespace fixes the issue as well and is much less code churn. 

https://github.com/llvm/llvm-project/pull/136019