KT-4027 No type name completion in an incomplete generic extension function declaration

KT-2940 No completion in the receiver type argument position

 #KT-4027 Fixed
 #KT-2940 Fixed

idea/testData/completion/basic/common/GenericExtensionFunReceiver2.kt

@@ -0,0 +1,11 @@
+class Foo{}
+
+fun foo() {}
+
+fun <T> <caret>
+
+// INVOCATION_COUNT: 1
+// EXIST: Foo
+// EXIST: String
+// EXIST: Set
+// ABSENT: foo