[llvm] Reland [SimplifyCFG] Delete the unnecessary range check for small mask operation (PR #70542)

[via llvm-commits]

vfdff wrote:

Thanks @zmodem for your suggestion, I add a new caset `switch_lookup_with_small_i1_unraachable` to make sure the default branch unreaachable, which list` all the possible cases` of switch.

https://github.com/llvm/llvm-project/pull/70542