Use site_url to build form cache

[alanhartless]

Please be sure you are submitting this against the staging branch.

Q	A
Bug fix?	y
New feature?
Automated tests included?
Related user documentation PR URL
Related developer documentation PR URL
Issues addressed (#s or URLs)
BC breaks?
Deprecations?

Description:

When URLs are generated through the router in a web request, the router uses the request to set host, etc. This is normally fine except when you can access the site through multiple URLs (http, https). For forms, the HTML is cached with an action of whatever URL is used to access Mautic. If this mismatches the site_url, the form will fail to submit.

Steps to reproduce the bug:

1. Edit config file's site_url to some other host (it can be bogus)
2. Clear the cache
3. Create a new form
4. View the form's manual copy HTML and look for the form's action
5. Notice that it is the host you used to access Mautic and not what is set in site_url

Steps to test this PR:

1. Repeat and this time the host will match site_url instead

[alanhartless]

This has been reviewed by our team in production for a while now so labeling as pending test confirmation.

[kuzmany]

This PR resolve same issue #6752
Should close then?

[npracht]

It works thanks.

[heathdutton]

This doesn't appear to work for any dev site that isn't at root.
For example, all mautibox PRs now redirect haphazardly:
https://mautibox.com/index_dev.php/7210/s/dashboard

Can we remove this? I don't see it as needed.

[kuzmany]

@alanhartless what do you think?

[alanhartless]

It'll be a pain for developing if none of the URLs you click on has index_dev.php in it. I'd rather fix this to work with paths than just remove it.

[heathdutton]

Agreed... will you be doing that or should I?

[alanhartless]

#7572