[clang] [analyzer][Solver] Early return if sym is concrete on assuming (PR #115579)

[Ding Fei via cfe-commits]

danix800 wrote:

It is unstable ordering of elements from DenseMap/Set.

This PR actually breaks the recursive fixpoint simplification algorithm of the eq class.

One thing left which confused me is that why no randomness is observed when compiled
by gcc on linux, purely out of coincidence?

https://github.com/llvm/llvm-project/pull/115579