Fix appearance of rename input

Also sets the width of the directory rename input in the same way as the file input (which is the same way jstree would do it).

The fundamental problem here was that the theme styles were taking precedence over the tree styles.

Fixes:

* #9201 
* #9210 
* #9262 

Note: at the moment, you can still see the height of the entry change a little bit, which didn't happen on the old tree. I'm not sure why that is. It could be that the line height of the non-input nodes is taller in the new tree than the old.
I was just bringing this branch up to date with master and then noticed that I'm wrong... what you've done here *is* equivalent to the old one. Sorry for injecting confusion...