Loads the library at the given uri into this isolate.
WARNING: You are strongly encouraged to use Isolate.spawnUri instead when possible. IsolateMirror.loadUri should only be used when synchronous communication or shared state with dynamically loaded code is needed.
If a library with the same canonicalized uri has already been loaded, the existing library will be returned. (The isolate will not load a new copy of the library.)
This behavior is similar to the behavior of an import statement that appears in the root library, except that the import scope of the root library is not changed.
Future<LibraryMirror> loadUri(Uri uri);