More efficient code completion + fixed a few bugs

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

@@ -0,0 +1,11 @@
+class C {
+    class Nested
+    inner class Inner
+}
+
+fun foo(c: C) {
+    c.<caret>
+}
+
+// ABSENT: Nested
+// ABSENT: Inner