[clang] [Clang][Sema] Print more static_assert exprs (PR #74852)

[via cfe-commits]

sethp wrote:

I think this change is useful enough on its own that I'd like us to consider merging it: to me, teaching the compiler to do additional diffing or further clarifying the structure of complicated sub-objects feel like they'd benefit from having this work as a fallback. We could then build up from concrete examples of "it would be nice if the compiler diff'd here", and rely on the much more capable (and domain-aware) programmers to use the complete evaluation result for solving the general case.

That said, I'm curious if there's an upper limit we ought to set here on the size of the string: copy & paste work fine for hundreds or even thousands of characters, but if someone `static_assert`s on a multi-GB `const char*`, they might be in for a bit of trouble.

https://github.com/llvm/llvm-project/pull/74852