Make shortcut add and edit form titles better

Problem/Motivation

#2416987: Fix UI regression in the menu link form → found (and had code to fix)
that the shortcut add and edit form title would be better if it used the word shortcut on them.

Proposed resolution

Use shortcut in page title
Merge "list shortcuts" page into "edit shortcut set" page to improve usability

Remaining tasks

Postponed on 📌 [policy] Determine design for forms that have multiple actions Active
Implement tweaks from 📌 Separate the menu settings from the 'add link' button Postponed

User interface changes

Yes.
It'll merge "list shortcuts" page into "edit shortcut set" page

API changes

No more shortcut links overview page.