Fix bug with member extensions with explicit receiver

Co-authored-by: Ilya Kirillov <ilya.kirillov@jetbrains.com>

idea/idea-completion/testData/basic/common/primitiveCompletion/classFieldsAndFunctions.kt

@@ -2,6 +2,9 @@ class A {
     fun aa() {}
     val aaa = 10
 
+    fun Int.extFun() {}
+    fun Int.extVal() {}
+
     fun test() {
         <caret>
     }
@@ -9,3 +12,6 @@ class A {
 
 // EXIST: aa
 // EXIST: aaa
+// ESIST: test
+// ABSENT: extFun
+// ABSENT: extVal