[llvm] [LV] Add tests showing incorrect handling of large vscale ranges (NFC). (PR #219290)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

Can you explain what the incorrect behaviour is? I interpret this to mean broken but the test implies this is a performance issue? Is it the case you know the code has an overflow bug and this is just the effect?

https://github.com/llvm/llvm-project/pull/219290