[llvm] [SystemZ][z/OS] Show instruction encoding in HLASM output (PR #181904)

[Fangrui Song via llvm-commits]

MaskRay wrote:

We need two patches

* Extract the class to llvm/include/MC/MCAsmStreamer.h. https://github.com/llvm/llvm-project/pull/183763 tried to do this but did this in a wrong way (the base branch should be `main`). In addition, don't unnecessarily extract functions llvm/lib/MC/MCGNUAsmStreamer.cpp 
* This patch should set the base branch to the first patch's branch. This patch will contain HLASM specific changes, and don't contain MCAsmStreamer.cpp refactoring.

https://github.com/llvm/llvm-project/pull/181904