[llvm] [TableGen][NFC] Remove MultiClass argument and Scoper in QualifyName (PR #69297)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

> I wonder if `Record` should have an IsMulticlass field to avoid the need for the IsMC boolean argument?

`multiclass` is represented by C++ class `MultiClass`, where there is a `Record` field `Rec`. I think this can be done, but some refactors are needed. I Will push another PR for it later.

https://github.com/llvm/llvm-project/pull/69297