Wrong email confirmation link sent in case the mail was changed in user admin

[ocean90]

If a user isn't a member of a site in a multisite install they can change their profile settings at wp-admin/user/profile.php.
If the email is changed send_confirmation_on_profile_email() will send a mail with a confirmation link. But the function is using admin_url() for the link which ignores the wp-admin/user/ part.

[ocean90]

Originally reported by @sippis, see ​https://wordpress.slack.com/archives/meta/p1454791322002714.

[ocean90]

In 36503:

Users: Use self_admin_url() for the email change confirmation link.

Prevents sending users to wp-admin/profile.php if they only have access to wp-admin/user/profile.php.

Fixes #35766.