[clang] [clang][analyzer] Stable order for SymbolRef-keyed containers (PR #121551)

[Arseniy Zaostrovnykh via cfe-commits]

necto wrote:

@steakhal @NagyDonat, I revised and improved #121347.
To facilitate review, I broke the change down into 3 self-contained commits. let tests pass after each of them.
I re-evaluated this version and discovered no difference in the analysis outcome.

https://github.com/llvm/llvm-project/pull/121551