[llvm] [GlobalISel] Combine [a, s, z]ext of undef into 0 or undef (PR #117439)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

The market share of unprotected `Builder.buildUndef` in CombinerHelper.cpp is really high. I am starting to see the point.

https://github.com/llvm/llvm-project/pull/117439