feat(graphics): add idle management configuration option

[kajusnau]

Description of changes

1. Add Idle Management Config Option to options.ghaf.profiles.graphics:
   • Defaults to true to enable swayidle idle management

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
  • Tested on Dell Latitude x86_64
• 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:
  • AGX
  • NX
  • x86_64
• Is this a new feature
  • List the test steps to verify:
• If it is an improvement how does it impact existing functionality?
  • Allows choosing whether to enable or disable idle management for particular targets

[kajusnau]

Edit:

• Removed conflicting graphics.labwc.autolock.enable assignment from orin target
• Removed redundant graphics.labwc.autolock.enable assignments from user trial profiles