[llvm] [LoopDist] Add metadata for checking post process state of distribute… (PR #153902)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur commented:

> Ok, I can do that. It's functionally equivalent for our purposes.

If there is a use for the number, we can add it, but a rationale is missing. The rationale would also determine how to interpret the number. Otherwise use the simplest data structure that does the job.

Please also add documentation to the language reference. Yes, `llvm.loop.isvectorized` is missing already.

https://github.com/llvm/llvm-project/pull/153902