Fixed extension functions being grayed in import statement completion

#KT-5627 Fixed

idea/idea-completion/testData/basic/multifile/InImport/InImport.dependency.kt

@@ -0,0 +1,7 @@
+package second
+
+fun String.extensionFun(){}
+val Int.extensionVal: Int get() = 1
+
+fun topLevelFun(p: (String, Int) -> Unit){}
+val topLevelVal: Int = 1

idea/idea-completion/testData/basic/multifile/InImport/InImport.kt

@@ -0,0 +1,8 @@
+package first
+
+import second.<caret>
+
+// EXIST: { itemText: "extensionFun", tailText: "() for String in second", attributes: "" }
+// EXIST: { itemText: "extensionVal", tailText: " for Int in second", attributes: "" }
+// EXIST: { itemText: "topLevelFun", tailText: "(p: (String, Int) -> Unit) (second)", attributes: "" }
+// EXIST: { itemText: "topLevelVal", tailText: " (second)", attributes: "" }