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

[Baranov Victor via cfe-commits]

vbvictor 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`? 

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