[llvm] [DebugInfo] Clone dbg.values in SimplifyCFG like normal instructions (PR #72526)

[Jeremy Morse via llvm-commits]

jmorse wrote:

/me squints -- right you are, I hadn't spotted that those dbg.values should actually be dropped. I think this change doesn't make anything worse seeing how all the source-locations are dropped too, and it removes a special-debug-juggling location, which is desirable for RemoveDIs. Pushed up to the compile-time-tracker for testing, just in case.

This is actually something moderately important we're going to have to track -- it exposes one of our favourite pieces of IR, "what happens when we merge a PHI-value variable to be calculated by a select in a single block".

https://github.com/llvm/llvm-project/pull/72526