Sema: Don't generate OneWayEqual constraints for pattern bindings

I had to revert #78301 to fix
rdar://143338891.

This now brings back the change, but without deleting code; instead,
it's guarded by the -disable-optimized-restrictions flag. Once the
flag is removed, I will once again completely delete OneWayEqual
constraints.

Author: slavapestov

lib/Sema/CSGen.cpp

@@ -2704,7 +2704,8 @@ namespace {
         // type variable and a one-way constraint to assign it to either the
         // deduced type or the externally-imposed type.
         Type oneWayVarType;
-        if (bindPatternVarsOneWay) {
+        if (CS.getASTContext().TypeCheckerOpts.DisableOptimizedRestrictions &&
+            bindPatternVarsOneWay) {
           oneWayVarType = CS.createTypeVariable(
               CS.getConstraintLocator(locator), TVO_CanBindToNoEscape);