Pass KProperty instances to property delegates

Inherit KProperty from PropertyMetadata, cache corresponding KProperty objects
instead of PropertyMetadataImpl objects, add support for properties with 2
receivers

compiler/testData/codegen/box/delegatedProperty/propertyMetadataEqualsHashCodeToString.kt

@@ -1,36 +0,0 @@
-import java.util.HashSet
-
-class A {
-    val foo: String by O
-    val Int.foo: String by O
-
-    fun foo42() = 42.foo
-}
-
-val foo: String by O
-val Int.foo: String by O
-
-object O {
-    val metadatas = HashSet<PropertyMetadata>()
-
-    fun getValue(t: Any?, p: PropertyMetadata): String {
-        metadatas.add(p)
-        return ""
-    }
-}
-
-fun box(): String {
-    A().foo
-    A().foo42()
-    foo
-    42.foo
-
-    if (O.metadatas.size != 1)
-        return "Too many different PropertyMetadata instances: ${O.metadatas}"
-
-    val m = O.metadatas.iterator().next()
-    if (m.toString() != "PropertyMetadata(name=foo)")
-        return "Wrong toString(): $m"
-
-    return "OK"
-}