[clang] [Clang] [NFC] Introduce `ConstDynamicRecursiveASTVisitor` (reland) (PR #124821)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > I don't think `.template` is incorrect. Maybe you hit #96364 or somethink @sdkrystian
> 
> Yeah, at first I thought it was required, apparently it’s not. GCC and Clang accept both, but I also don’t think it’s incorrect, so... I’m still somewhat confused about this

It's what I thought at first as well, but because the post-commit bots were falling over on parsing, it seemed like it was the most likely suspect for what's going wrong.

I really hope we're not in a situation where we need the `template` for some bots and can't have it for other bots.

Btw, precommit CI failures on Windows look unrelated to this PR.

https://github.com/llvm/llvm-project/pull/124821