Do not focus or blur editor of it is already focussed or blurred

[ellatrix]

I am seeing some strange things with selection inside an Editable.

• Select a piece of text, then click in the Editable. Expected: caret moves to selected position. Actual result: selection is kept (though quickly disappears, then comes back).
• Sometimes, pressing to pointer to select text, and moving it, the caret moves with the pointer instead of starting a selection. I can't reproduce this consistently, but certainly happens when you try a few times.

Both if these issues seem to be caused by us continuously focussing the editor even though it is already focussed. To fix this, we should only update the focus/selection when it is necessary.

[youknowriad]

This PR seems to fix a lot of selection issues, nice work 👍