Rename: this object, receiver argument -> dispatch receiver, extension receiver

compiler/testData/resolvedCalls/hasBothDispatchAndExtensionReceiversWithoutExplicitReceiver.kt

@@ -0,0 +1,13 @@
+class A {
+    fun B.foo() {}
+}
+
+trait B
+
+fun bar(a: A, b: B) {
+    with (a) {
+        with (b) {
+            <caret>foo()
+        }
+    }
+}