Sync: Add protocol to raw urls

[ebinnion]

There's been an uptick in support tickets where connections are breaking after the site switches to https. This seems to have started with 5.2 or 5.3, likely when we deployed this PR:

#5852

In that PR, we began syncing the raw home/siteurl values from the DB or from the WP_HOME and WP_SITEURL constants. As part of that work, since we were no longer calling functions like get_home_url() which will set the protocol to https when is_ssl() is true, the https change wasn't getting picked up.

This PR should fix that by adding the is_ssl() check and setting the protocol to https if so.

To test:

• Run tests

[enejb]

@ebinnion can you explain when we sync those values. The problme that I see with this solution is that if the site has the value set in the DB but the user is able to visit the same site under both urls. https and http then the problem could still happen that the scheme is switching. (but I am not sure if the previous PR was trying to address that or not)
Maybe we could help the user somehow.

Ask them to set define('FORCE_SSL_ADMIN', true); to be true or something like that. Which would help redirect them to https if they are already visiting the site with that.

The code looks good and makes sense to me.

[ebinnion]

We sync those values when we sync callables, which happens when the user visits wp-admin I believe.

The issue here isn't the protocol normalization, or that the value flip-flops. The issue is that the site isn't swapping from http to https at all. Likely because users are using methods such as htaccess or a redirect plugin, as opposed to updating the home/siteurl values in the database.

We could tell users to update the values in the db or the constant to have https, but I'm not sure that's practical since it still results in the user getting in touch with support and support then walking them through that.

[oskosk]

LGTM!