Imports on paste: do not suggest to import already imported extensions

idea/testData/copyPaste/imports/AlreadyImportedExtensions.dependency.kt

@@ -0,0 +1,3 @@
+package dependency
+
+fun String.extensionFun() {}

idea/testData/copyPaste/imports/AlreadyImportedExtensions.expected.kt

@@ -0,0 +1,8 @@
+fun foo() {
+    s.extensionFun()
+    for (i in s.indices) {
+        val pair = s to null
+        val s1 = s + "1"
+    }
+
+}

idea/testData/copyPaste/imports/AlreadyImportedExtensions.expected.names

@@ -0,0 +1 @@
+

idea/testData/copyPaste/imports/AlreadyImportedExtensions.kt

@@ -0,0 +1,10 @@
+// RUNTIME
+// ALLOW_UNRESOLVED
+
+fun foo(s: String) {
+<selection>    s.extensionFun()
+    for (i in s.indices) {
+        val pair = s to null
+        val s1 = s + "1"
+    }
+</selection>}

idea/testData/copyPaste/imports/AlreadyImportedExtensions.to.kt

@@ -0,0 +1,3 @@
+fun foo() {
+<caret>
+}