[AMDGPU] Update code object metadata for kernarg preload
Tracks the registers that explicit and hidden arguments are preloaded to
with new code object metadata.
IR arguments may be split across multiple parts by isel, and SGPR tuple
alignment means that an argument may be spread across multiple
registers.
To support this, some of the utilities for hidden kernel arguments are
moved to `AMDGPUArgumentUsageInfo.h`. Additional bookkeeping is also
needed for tracking purposes.
