Add TextEditorElement::setUpdatedSynchronously

To allow testing of async editor rendering in packages. This is helpful
for overlay decorations which behave differently when rendering is
async.

Signed-off-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Always focus pane element when pane model is activated

Signed-off-by: Max Brunsfeld <maxbrunsfeld@gmail.com>