KT-4727 J2K: Convert Java code copied from browser or other sources

#KT-4727 Fixed

idea/testData/copyPaste/plainTextConversion/WholeFile.txt

@@ -0,0 +1,8 @@
+import java.util.ArrayList;
+
+class JavaClass {
+    void foo() {
+        ArrayList<String> list = new ArrayList<String>();
+        list.add(1);
+    }
+}