[clang] More fixes for P3144R2 implementation (PR #149406)

[Harald van Dijk via cfe-commits]

hvdijk wrote:

Release note added, and diagnostics updated to use `%select{struct|interface|union|class|enum}` based on `getTagKind()` which is already used for other diagnostics too (look for `|interface|` in the same file).

I do take your point about `pointer-to-'void'` being clumsy wording, despite it already being used, and will have a think about how to rephrase, but I want to avoid the warning suggesting that it is an error to delete a pointer to incomplete types (that was wrong and why I started looking at this in the first place).

https://github.com/llvm/llvm-project/pull/149406