Finalize Proxy Screens Page view

[jarolrod]

We've implemented, in bitcoin-core/gui-qml#223, a version of the Proxy screen based off a design found in the old figma file which hadn't been finalized.

Can we get this finalized and into the new&main design file?

[GBKS]

Re-using this old issue to track proxy screen changes. @pablomartin4btc is working on an updated implementation with PRs 430 and 433. Once that is done, let's revise the design files and docs again to ensure it all matches.