Implement type inference for PropertySet.

pkg/front_end/testcases/inference/property_set_bad_setter.dart.strong.expect

 library test;
 import self as self;
 import "dart:core" as core;
 
 class A extends core::Object {
-  field core::int x = 2;
   constructor •() → void
     : super core::Object::•()
     ;
+  set x() → void {}
 }
-static method test5() → dynamic {
-  self::A a1 = new self::A::•();
-  a1.x = "hi";
-  self::A a2 = new self::A::•();
-  a2.x = "hi";
+static method f(self::A a) → void {
+  core::int x = a.{self::A::x} = 0;
 }
 static method main() → dynamic {}