[CSFix] Allow diagnose to accept a solution to diagnose

Instead of always applying solution back to constraint system
before diagnostics, let's pass solution directly to `ConstaintFix::diagnose`
method to be used by `FailureDiagnostic` which paves a way for
stateless diagnostics.

lib/Sema/CSApply.cpp

@@ -7326,7 +7326,8 @@ bool ConstraintSystem::applySolutionFixes(const Solution &solution) {
         auto *primaryFix = fixes[0];
         ArrayRef<ConstraintFix *> secondaryFixes{fixes.begin() + 1, fixes.end()};
 
-        auto diagnosed = primaryFix->coalesceAndDiagnose(secondaryFixes);
+        auto diagnosed =
+            primaryFix->coalesceAndDiagnose(solution, secondaryFixes);
         if (primaryFix->isWarning()) {
           assert(diagnosed && "warnings should always be diagnosed");
           (void)diagnosed;