Generate separate anonymous class for each property reference

Each property reference obtained by the '::' operator now causes back-end to
generate an anonymous subclass of the corresponding KProperty class, with the
customized behavior. This fixes a number of issues:

- get/set/name of property references now works without kotlin-reflect.jar in
  the classpath
- get/set/name methods are now overridden with statically-generated property
  access instead of the default KPropertyImpl's behavior of using Java
  reflection, which should be a lot faster
- references to private/protected properties now work without the need to set
  'accessible' flag, because corresponding synthetic accessors are generated at
  compile-time near the target property

 #KT-6870 Fixed
 #KT-6873 Fixed
 #KT-7033 Fixed

compiler/testData/codegen/boxAgainstJava/reflection/mapping/javaFields.kt

@@ -10,8 +10,8 @@ fun box(): String {
     val s = J::s
 
     // Check that correct reflection objects are created
-    assert(i.javaClass.getSimpleName() == "KProperty1Impl", "Fail i class")
-    assert(s.javaClass.getSimpleName() == "KMutableProperty1Impl", "Fail s class")
+    assert(i !is KMutableProperty<*>, "Fail i class: ${i.javaClass}")
+    assert(s is KMutableProperty<*>, "Fail s class: ${s.javaClass}")
 
     // Check that no Method objects are created for such properties
     assert(i.javaGetter == null, "Fail i getter")