[llvm] [MISched] Extend overridePostRASchedPolicy to support per-function scheduling direction (PR #149297)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> 1. Should we change `overrideSchedPolicy` as well?

I also think we should apply this change on pre-RA scheduler in this patch.

https://github.com/llvm/llvm-project/pull/149297