Remove 'Quick settings' - Streamline access to 'All settings'

### Your use case

Clicking the settings cog (bottom-left) opens the “Quick Settings” popover. From there, click “All Settings” to access it.

#### What would you like to do?
Clicking the cog opens 'All settings', directly.
#### Why would you like to do it?
Less friction to end goal - exploring configuration options.
#### How would you like to achieve it?
Relocate the buttons in the "Quick settings" popover then make clicking the cog open "All settings".
- Developer tools - moved to be the last item in the All settings list, retaining its red colouring.
- Light and dark theme - placed in the user menu, top left.

### Have you considered any alternatives?

1. Make 'Quick settings' toggle-able.
2. Make it configurable.
- You can choose which setting to put in the 'Quick settings' popover.

### Additional context

_No response_