idle: use cosmic-idle, allow runtime idle config adjustment

[kajusnau]

Description of Changes

1. Idle config changes:
   • Removed swayidle
   • Re-enabled COSMIC Settings 'Power & battery' page
     • This page should now be fully functional
     • Allows runtime adjustment of system idle behavior
   • Adjusted idle nix config in graphics profile to only allow enabling/disabling
     Up for debate:
     Disabling only sets the timeouts to 0 by default, but they can still be overridden by the user at runtime.
     Is it worth keeping the enable/disable option?
2. Adjusted suspend configuration:
   • Moved allowSuspend option to power-manager namespace, for easier maintainability and clarity
   • Adjusted some targets, where suspend should be disabled, accordingly.
3. Other: Adjusted brightness shortcut to use COSMIC settings dbus

Removed functionality:

• Swayidle
• Idle notifications, informing the user of incoming session lock/suspension. Replaced by cosmic-idle's fade-to-black

Type of Change

• New Feature
• Bug Fix
• Improvement / Refactor

Related Issues / Tickets

Checklist

• Clear summary in PR description
• Detailed and meaningful commit message(s)
• Commits are logically organized and squashed if appropriate
• Contribution guidelines followed
• Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• 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

Testing Instructions

Applicable Targets

• Orin AGX aarch64
• Orin NX aarch64
• Lenovo X1 x86_64
• Dell Latitude x86_64
• System 76 x86_64

Installation Method

• Requires full re-installation
• Can be updated with nixos-rebuild ... switch
• Other:

Test Steps To Verify:

1. Verify idle timeouts work as expected according to these timers:
   • 5 mins - screen off and session locked
   • 15 mins - suspend on AC (if suspend is enabled)
   • 15 mins - suspend on battery (if suspend is enabled)
2. Verify idle timeouts can be interrupted by user activity
3. Adjust idle timeouts in the COSMIC Settings -> Power & battery page, verify adjustments take effect
4. (Optional) adjust power profiles via COSMIC Settings -> Power & battery. Adjustments should take effect immediately, same as with the battery applet.
5. Verify suspension is still disabled on s76 darp11

[kajusnau]

Fixed allowSuspend not being set for host config, defaulting to false.

Suspension should now work properly wherever it is enabled.

[milva-unikie]

Tested on Darter Pro and Lenovo X1 (new image)

All good!

• Laptop is locked and the screen turns off after 5 minutes.
• Lenovo X1: Laptop suspends after 15 minutes.
• Darter Pro: Suspension is disabled, the screen stays off but the laptop does not suspend.
• User can change the timing of the screen off / suspend in the settings.
• Activity on the laptop resets the idle timeouts.
• Power profiles work.
• Found one nice surprise: Power & battery page shows the battery of connected USB devices.

Pre-merge pipeline has failures on laptops because swayidle is removed. Test automation changes are ready and tested tiiuae/ci-test-automation#637. They need to be merged together with this @brianmcgillion.