[clang] [clang-tools-extra] [clang] Make 'fileScopeAsmDecl' matcher public (PR #165319)

[Davide Cunial via cfe-commits]

capitan-davide wrote:

> I suspect we didn't update `clang/docs/LibASTMatchersReference.html` before thus big diff occurred.
> 
> Could we separate two patches because it brings a lot of changes in one go? First re-run `clang/docs/LibASTMatchersReference.html` and we can land it as NFC and then we would land this "fileScopeAsmDecl" patch quite easy.
> 
> I can do first patch by myself if you don't wish to spend time on in. If so, could you show the command to build `LibASTMatchersReference.html`?

I also was surprised, the script for `clang/docs/LibASTMatchersReference.html` is called [dump_ast_matchers.py](https://github.com/llvm/llvm-project/blob/main/clang/docs/tools/dump_ast_matchers.py). Probably was not run for some time..

https://github.com/llvm/llvm-project/pull/165319