Bring some JS and CSS code from spree_backend related to orders admin

[luisramos0]

What? Why?

Continues #4595

What should we test?

• Verify the edit product page has the usual style and positioning of elements.
• Verify you can add, edit and remove images from a product
• Verify the orders search page and the order edit page have the usual style and positioning of elements.
• In the list of payments of an order, make sure the outstanding balance tag is in the correct place with correct style

Release notes

Changelog Category: Changed
Bring javascript code related to orders from spree_backend so we can make OFN independent of Spree.

[luisramos0]

I rebased and added a dependency needed (admin/globals/variables.scss which is already added on another PR) to make the precompilation process work here.
Ready for testing.

[lin-d-hop]

This is looking good.
Tested all steps and compared to UK production. Everything is exactly as it should be.
Ready to go!

[lin-d-hop]

@luisramos0 except now there is a conflict

[luisramos0]

it's a tiny conflict in the all css file, I dont think this can create problems, I will merge now.