[llvm] [GlobalIsel] Combine zext of trunc (episode II) (PR #108305)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

The first combine used `Helper.replaceSingleDefInstWithReg` and ran on the `AMDGPURegBankCombiner`. I prefer the lambda matchinfo, which cannot run after regbank select. Now, I enabled both.

https://github.com/llvm/llvm-project/pull/108305