[clang] [libcxx] [llvm] Reapply "[Clang] Implement resolution for CWG1835 (#92957)" (PR #98547)

[Krystian Stasiowski via llvm-commits]

sdkrystian wrote:

> > We already do that :) the problem is when what follows `A` _doesn't_ unambiguously look like a template argument list:
> 
> Sure, but before CWG1835, we would perform the lookup anyway and treat the `<0>` as a template argument list, even if it isn't unambiguously a template argument list.
> 
> So we could try to do this just as well if A doesn't unambiguously look like a template argument list.
> 
> That seems better than not trying to apply the new rule at all.

I'm not sure I follow. If we "treat the `<0>` as a template argument list, even if it isn't unambiguously a template argument list.", then aren't applying CWG1835 at all. 

https://github.com/llvm/llvm-project/pull/98547