[clang] [Clang] Fix Microsoft ABI inheritance model when member pointer is used in a base specifier (PR #91990)

[Max Winkler via cfe-commits]

https://github.com/MaxEW707 approved this pull request.

LGTM.

@MitalAshok I noticed in your commit messages you mentioned reworking -fcomplete-member-pointers. Will that include fixing clang incorrectly warning when an inheritance model is explicitly specified. Godbolt for reference: https://godbolt.org/z/rYaWz6sra.

https://github.com/llvm/llvm-project/pull/91990