Add a label to the URL field in the Publishing Flow panel

[afercia]

Description

The Post URL field in the Publishing Flow panel is unlabelled. This PR adds a visible label. Also simplifies a bit the text for the Scheduled posts. I know there are pending proposal to improve and add features to the publishing flow so this part will be very likely improved and iterated. The most important thing in this PR is the input field label.

Screenshots

Before:

After:

Note 1:
the sentence "The post address will be:" is not appropriate anyways, as a post can be of different types: post, page, or a custom post type. To keep things simple I've just removed it in favor of "What’s next?".

Note 2:
since the URL field is readonly, I'd suggest to communicate to users it can't be edited. Usually in WordPress this is done by using a light gray background. Something like in the screenshot below or a lighter gray could work:

Fixes #9535

[jorgefilipecosta]

Can we use Text Control component to simplify this logic? (it automatically generates the ids).

[jorgefilipecosta]

Hi @afercia thank you for looking into this issue. I did some tests, and things worked correctly 👍 From the code point view the changes look good, as a possible improvement we may check if Text Control component can be used here to simplify things and promote reusability.

[afercia]

Hi @jorgefilipecosta, thanks. Updated to use TextControl. I've also added a light grey background to the readonly field. I've opted for $light-gray-400 #e8eaeb because it's the closest one to the grey used in core (#eeeeee).

One thing I don't like so much in the TextControl component is that the label element, by default, is styled as display: block. Thus, all the available width is clickable:

This could be confusing for users, especially when the clickable area is very large. Should go in a separate issue though.

Note:
I see a few warnings (not recognized props on DOM elements) when the Publish panel opens, seem unrelated to me and they happen also on master.

[karmatosed]

Looks like there are some conflicts on this. I am approving design wise but we would need to get those resolve, thanks!

[jorgefilipecosta]

I rebased this PR (resolving the conflict) so the local tests take into account changes occurred in parallel.
The tests went well and the code looks good to me. Thank you for iterating on this changes 👍

[afercia]

Thank you Jorge.

[karmatosed]

Should we consider URL over address? How does address scale for all situations? I'm not debating having the word as much as having some copy iterations.

[chrisvanpatten]

@karmatosed I also wonder if it's even better to switch over to "Permalink" since that's a standard and familiar WP term already used in a few places.