labwc: enable audio controls, fix wifi status script

[humaidq-tii]

Enables the media keys for volume up, down, and mute toggling.

Also now the wifi-signal-strength script is checked by shellcheck, all shellcheck issues are fixed, including bugs when netvm is rebooted and signal strength 0 not showing properly.

Description of changes

• Media keys now work for volume up, volume down, and mute.
  • Volume step is 5%.
• Brightness step is now 5% instead of 10%.
• wifi-signal-strength script fixes
  • When net-vm reboots, host key check used to fail (even with it set to no). This is now fixed, so status should continue to update after net-vm reboots.
  • When signal strength was <30, it used to print "signal0" instead of icon. Now proper icon should be shown.
  • Script uses writeShellApplication which means it is run through shellcheck.
  • Shellcheck issues are fixed.

Checklist for things done

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

Testing

• Test volume keys (volume up, down, mute).
  • There might be small delay for these key presses, unlike brightness which is instant.
• Reboot net-vm, the status for wifi should continue to update properly after it is back up.

[humaidq-tii]

Tested with external display, no issues with running out of resources/memory.

[milva-unikie]

Tested on Lenovo-X1 (nix build github:humaidtii/ghaf/audio-ctrl-wifi-fix#lenovo-x1-carbon-gen11-debug)

Found issues:

• Mute button (F1) works, but the led stays on when mute is turned off. At least on my other Lenovo laptop the led is off when mute is off.
• Network settings don't open after net-vm is restarted from host with sudo systemctl restart microvm@net-vm.service -> can't connect back to wifi and check if it works.
• There is still something weird happening when wifi strength is under 30 %.

Working:

• Volume up and down buttons work. Confirmed in audio-vm with pamixer --get-volume-human that the change is always 5 % and goes from 0 % to 100 %.
• Brightness up and down buttons work. There are 20 steps between the brightest and 0.
• Internal speakers & microphone and 3,5 mm headset both work in chromium and element.
• Test-automation passes.
• Performance ok.

[milva-unikie]

Confirmed on Lenovo-X1 that network settings can now be opened after restarting net-vm and connecting back to wifi works.