[llvm] MCExpr-ify SIProgramInfo (PR #88257)

[Thurston Dang via llvm-commits]

thurstond wrote:

I think this may have broken a buildbot:

https://lab.llvm.org/buildbot/#/builders/5/builds/43260/steps/9/logs/stdio

```
  LLVM-Unit :: MC/AMDGPU/./AMDGPUMCTests/SIProgramInfoMCExprsTest/TestDeathHSAKernelEmit

[  DEATH   ] /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUHSAMetadataStreamer.cpp:464:38: runtime error: reference binding to null pointer of type 'const llvm::SIMachineFunctionInfo'
```

https://github.com/llvm/llvm-project/pull/88257