Auto merge of #90050 - michaelwoerister:fix-vtable-debug-name-crash-90019, r=wesleywiser

Erase late-bound regions before computing vtable debuginfo name.

Fixes #90019.

The `msvc_enum_fallback()` for computing enum type names needs to access the memory layout of niche enums in order to determine the type name. `compute_debuginfo_vtable_name()` did not properly erase regions before computing type names which made memory layout computation ICE when encountering un-erased regions.

r? `@wesleywiser`