[clang] [clang] [diagnostics] Stable IDs for Clang diagnostics (PR #168153)

[Dave Bartolomeo via cfe-commits]

dbartol wrote:

@AaronBallman I went ahead and implemented the support for explicitly specifying the stable ID, and for listing previous stable IDs, in a [separate PR](https://github.com/dbartol/llvm-project/pull/2) against this PR. Any thoughts about this approach to managing stable IDs over time?


https://github.com/llvm/llvm-project/pull/168153