[clang] [clang] Enable C++17 relaxed template template argument matching by default (PR #89807)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> Here's a preprocessed file: [repro.zip](https://github.com/llvm/llvm-project/files/15250584/repro.zip)
> 
> I tried to reduce, and got rid of most of the test code and some of the stdexec code, but there's still a lot left. I hit the end of my timebox on that. Maybe creduce can do better.

That crashes with released clang 18.1.4 as well, same stack trace it seems.
```
Homebrew clang version 18.1.4
Target: arm64-apple-darwin23.4.0
```

Is it possible you may have reduced into a different bug?
It's always helpful in that case to keep testing with known good compiler while reducing.

https://github.com/llvm/llvm-project/pull/89807