Upstream systemd/udev is pulling our autosuspend hwdb, so if udev is new
enough, then there is no need to install the file. As such, add
auto-detection logic for the scenario.
This also changes the name of the option and the type to "feature".
This solves various problems:
1. It stays the same also if some drivers have been disabled
2. It uses a stable path for being imported by systemd
3. It is still checked for its validity by tests
4. It can be auto-generated using a simple command
