EWW: Add control panel, log out, and lock buttons, restyling

[kajusnau]

Description of changes

1. Added Control Panel and Power Menu Buttons:
   • New control panel button (called "Settings" now) added to the quick settings widget.
   • New log out and lock buttons added into the power menu widget.
   • More detailed design and composition currently in progress by UI designer.

2. Removed Shutdown and Log Out Apps From Launcher:

   • The shutdown and log out applications have been removed from the launcher to reduce redundancy.

3. Added Missing nm-applet UI Elements:

   • Missing UI elements for the nm-applet have been added.

4. Moved GTK Lock Style Definition To Its Own File:

   • This PR proposes moving all future style definitions to modules/desktop/graphics/styles for easier maintainability of the styles and the components that use them.
   • Other styles that could be moved include: gtkgreet, drawer, and ewwbar.

Checklist for things done

• Summary of the proposed changes in the PR description
• More detailed description in the commit message(s)
• Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• Contribution guidelines followed
• Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• PR linked to architecture documentation and requirement(s) (ticket id)
• Test procedure described (or includes tests). Select one or more:
  • Tested on Lenovo X1 x86_64
  • Tested on Jetson Orin NX or AGX aarch64
  • Tested on Polarfire riscv64
• Author has run make-checks and it passes
• All automatic Github Action checks pass - see actions
• Author has added reviewers and removed PR draft status
• Change requires full re-installation
• Change can be updated with nixos-rebuild ... switch

Instructions for Testing

• List all targets that this applies to:
  Lenovo X1
• Is this a new feature
  • List the test steps to verify:
    Can be tested on Lenovo X1 following usual installation or nixos-rebuild ... switch
• If it is an improvement how does it impact existing functionality?
  Listed in the description above.