RFC: Support setting ACPI platform profiles
This allows to switch between different ACPI platform profiles, such as "low power", "cool", "balaned", or "performance".
It adds an action that can be configured to switch automatically on AC (un)plugging or low power, as well as exposes that setting on DBus for a future Battery Monitor UI.
Haven't actually managed to get this working on my ThinkPad yet but it seemed straightforward enough to implement blindly.
- TODO: nicer UX ;)
- TODO: should we set some profile by default on AC or bat?