Support for import aliases in code completion

#KT-8848 Fixed

idea/idea-completion/testData/basic/java/importAliases/ExtensionFun.kt

@@ -0,0 +1,7 @@
+import kotlin.collections.firstOrNull as aaa
+
+fun foo() {
+    listOf(1, 2).aa<caret>
+}
+
+// EXIST: { lookupString: "aaa", itemText: "aaa", tailText: "() for List<T> (kotlin.collections.firstOrNull)" }