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

[Balazs Benics via cfe-commits]

steakhal wrote:

@danix800 Could you please have a look at the failed test, such that we could reapply this PR?
I reverted this soon after I realized the broken test is from this PR.

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