Populate Website URL profile field for the 1st user after install

[eclare]

When a new WP install is made, the 1st user (admin) could have the "Website" profile field (displayed at /wp-admin/profile.php) populated with the site's URL, as this will most likely be his choice anyway. This field is likely used by some plugins (for displaying author bio etc.), so we can make this a bit easier and less likely to be left empty.

[EFAREM]

Updates the user info just after the user is created

[EFAREM]

Tab :O

[darrenlambert]

Any thought on whether this should happen if the domain is localhost?
I assume, like all other URLs in the DB, that it will be updated when the site is moved to live.

[zachflauaus]

I agree with it just being "localhost" or whatever the local name of the site is on site create. Like you said, when you run a script to change URLs like searchreplacedb2.php or the like, it should just change things automatically.

[DrewAPicture]

Assigning to mark the good-first-bug as "claimed".

See 35778.2.diff​

[viralsampat]

Edit the user information after the user is created.

[SergeyBiryukov]

In 46989:

Users: When creating the first user on installation, populate the Website profile field with the site URL.

Skip setting the field if the user already exists, which is the case when the user tables are being shared among multiple sites.

Props EFAREM, eclare, darrenlambert, zachflauaus, viralsampat.
Fixes #35778.