[llvm] [InstCombine] Improve select equiv fold for plain condition (PR #83405)

[via llvm-commits]

vfdff wrote:

According [performace considerations](https://github.com/llvm/llvm-project/pull/83405#discussion_r1598042801), I deleted the support with multi-use select node and rebase to top upstream as the code conflicts.

https://github.com/llvm/llvm-project/pull/83405