[llvm] [Support][YamlTraits] Add quoting for keys in textual YAML representation (PR #88763)

[Jannik Silvanus via llvm-commits]

jasilvanus wrote:

> Unit tests in llvm/unittests/Support/YAML*?

Good point, thanks. I've added unit tests.

https://github.com/llvm/llvm-project/pull/88763