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

[Balazs Benics via cfe-commits]

https://github.com/steakhal commented:

@Xazax-hun I'm pretty happy with this PR, but I'm curious about your opinion on adding the `SymbolID Sym` member to the SymExprs.

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