[analyzer][NFC] Add LLVM_UNLIKELY to assumeDualImpl

[martong]

Summary

Aligned with the measures we had in D124674, this condition seems to be
unlikely.

Nevertheless, I've made some new measurments with stats just for this,
and data confirms this is indeed unlikely.

[martong]

clang/lib/StaticAnalyzer/Core/ConstraintManager.cpp

if (!P.first && P.second)
     return ConditionTruthVal(true);
   return {};
 }
 
 template <typename AssumeFunction>
 ConstraintManager::ProgramStatePair
 ConstraintManager::assumeDualImpl(ProgramStateRef &State,
                                   AssumeFunction &Assume) {
-  if (State->isPosteriorlyOverconstrained())
+  if (LLVM_UNLIKELY(State->isPosteriorlyOverconstrained()))
     return {State, State};
 
   // Assume functions might recurse (see `reAssume` or `tryRearrange`). During
   // the recursion the State might not change anymore, that means we reached a
   // fixpoint.
   // We avoid infinite recursion of assume calls by checking already visited
   // States on the stack of assume function calls.
   const ProgramState *RawSt = State.get();