[llvm] [ScalarEvolution] Avoid recursive proof blowup for recurrence starts (PR #225000)

[Justin Leong via llvm-commits]

justinleong22 wrote:

> Now that I think about it more carefully, this is ultimately still recursive, just more narrowly. Should it move from isKnownViaNonRecursiveReasoning to isKnownPredicate?

makes sense. I moved it to isKnownPredicate and needed a small range-check fix to keep an existing proof working. added a nested-start test as well

https://github.com/llvm/llvm-project/pull/225000