Use TextControl with label for post-publish permalink

[chrisvanpatten]

Fixes #9535.

Small change to the post-publish panel to use a TextControl with a "Permalink" label…

Also adjusted to use one of the grid-size variables.

It's a WIP because the click-to-select-text isn't working now that it's a TextControl instead of an input. Would love some help on that!

[chrisvanpatten]

This should be good for review!

Note: I replaced onFocus with onClick. This is due to some weird limitations around readonly inputs receiving focus. I am having a hard time finding a reference to this behaviour in any spec, but it's definitely A Thing™.

Even with the use of onClick instead of onFocus, the input content will receive focus in every case: keyboard navigation, clicking the label, or clicking the input.

[chrisvanpatten]

Hey @tofumatt — apologies for the ping, but this is ready for review :)

[chrisvanpatten]

Closing in favor of #9536 👍