[llvm] [CodeGen] Use shared RegClassInfo in basic, greedy and fast allocators (PR #226523)

[Michael Halkenhäuser via llvm-commits]

mhalk wrote:

@nkotikal FYI I am out-of-office for the next two weeks.
If this effort is important, please let me know and will try to spend some time & support (no promises) or feel free to pick this up :)

https://github.com/llvm/llvm-project/pull/226523