[llvm] [AMDGPU] Move AMDGPUTargetMachine into AMDGPUCodeGenPassBuilder(NFC) (PR #103720)

[Matt Arsenault via llvm-commits]

arsenm wrote:

Should only move TargetPassConfig. TargetMachine should stay in TargetMachine files. Failing that, I would rather merge CodeGenPassBuilder into the TM files 

https://github.com/llvm/llvm-project/pull/103720