[llvm] [TableGen][GISel] Extract common function for determining MI's regclass (PR #120135)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

There is also small refactoring (adding const qualifier to infer* methods), sorry about that.
I can extract this into a separate PR on request.


https://github.com/llvm/llvm-project/pull/120135