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

[Ding Fei via cfe-commits]

danix800 wrote:

> LGTM now. Thank you for this high quality patch. This isn't the first time, I remember. Excellent track record.

Thanks for your reviews and all of your kindness! @steakhal @NagyDonat 

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