[llvm] [TableGen][DecoderEmitter] Rework table construction/emission (PR #155889)

[Rahul Joshi via llvm-commits]

jurahul wrote:

For the switch op, I was thinking we can also encode a sorted table of values to be searched directly in the table and then do a binary search on that table instead of a linear search today (still better than sequential ops). That means the values and sizes need to be encoded directly and not as ULEB128 (to avoid decoding cost)...

https://github.com/llvm/llvm-project/pull/155889