[clang] -fsanitize=function: fix MSVC hashing to sugared type (PR #66816)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

It looks like the Itanium mangleTypeName() canonicalizes the type itself; should the MSVC mangleTypeName do the same thing?

https://github.com/llvm/llvm-project/pull/66816