JVM_IR: optimize delegation by property references

E.g. a statement like

    var x by ::y

is semantically equivalent to

    var x
      get() = y
      set(value) { y = value }

and thus does not need a full property reference object, or even a field
if the receiver is not bound.

 #KT-39054 Fixed
 #KT-47102 Fixed

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

@@ -0,0 +1,13 @@
+// WITH_RUNTIME
+// IGNORE_BACKEND: JS
+class C(var x: String)
+
+var x = "fail"
+var y by ::x
+var z by C("fail")::x
+
+fun box(): String {
+    y = "O"
+    z = "K"
+    return y + z
+}