Replace shortcut_requires_lock system with an alternate keybind when not locked

[Keavon]

Move the concept of shortcut_requires_lock to the input mapper as an alternate keybinding for Mac and standard platforms. This should also, therefore, apply to all keymappings not just the menu bar dropdowns. Display the alternate keybind when keylock is not active (i.e. fullscreen in a Chromium-based browser). Get rid of the (?) thing and perhaps the "Go fullscreen to access all hotkeys" text.

• [ ] Test on Windows
• [ ] Test on Mac