Support for import aliases in code completion

#KT-8848 Fixed

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

@@ -0,0 +1,7 @@
+import kotlin.io.DEFAULT_BUFFER_SIZE as BUFSIZE
+
+fun foo() {
+    BUF<caret>
+}
+
+// EXIST: { lookupString: "BUFSIZE", itemText: "BUFSIZE", tailText: " (kotlin.io.DEFAULT_BUFFER_SIZE)" }