[clang] [clang][analyzer] Stabilize path-constraint order by using alloc IDs (PR #121347)

[Arseniy Zaostrovnykh via cfe-commits]

necto wrote:

Hey, @steakhal, @NagyDonat 
I am working caching Z3 refutation query outcomes to reduce the number of flaky issues, and constraint order is important to maximize the cache-hit rate. Turns out, global constraint order is beneficial regardless query cache. Would you take a look?

BTW, a couple of points on the design of the change:
- I considered using simple incremental ids instead of allocator offsets, but found no advantage. Do you see any?
- Would it make sense to unify `SymbolData::Sym` and `SymExpr::AllocID`, and maybe get rid of the intermediary `SymbolData`?


https://github.com/llvm/llvm-project/pull/121347