[llvm] [MSVC][Demangling] Make Microsoft demangling more configurable (PR #202702)

[Aaron Ballman via llvm-commits]

https://github.com/AaronBallman commented:

Changes generally seem reasonable to me, but adding @rnk for a second set of eyes just to be sure.

https://github.com/llvm/llvm-project/pull/202702