[llvm] [SimplifyCFG]: Switch on umin replaces default (PR #164097)

[via llvm-commits]

kper wrote:

- I applied the suggestions
- I have added two new test cases for `[1,2,3]` and `[4,1,2,3]`
- I created a new overloaded method `SwitchInstProfUpdateWrapper::setDefaultDest` which takes the `CaseIt` instead of the BB. This method will update the weight accordingly.

https://github.com/llvm/llvm-project/pull/164097