liqctld: restructure package

Bug Fix

What does this MR do?

For proper python-package-based installation, need to use standard python package conventions for liqctld. This enables proper AUR installation.

Related issues

Checklist

• Application works as expected when running from source
• There are dependency changes
• Liquidctl device mock tests are successful (if applicable)
• Any needed documentation changes have been made
• This MR is ready to be merged