switch-on-port-available: Switch to headphones on unknown availability

switch-on-port-available: Switch to headphones on unknown availability

Since not all users will have environments that asks what they plugged
in when their hardware supports TRRS inputs but don't have impedance
sensing, let's emulate our previous default behaviour of enabling the
headphone port at least.

This can likely be improved so users can configure the module to select
for the device they are most likely to plug in (so an option to enable
just the microphone, or headphones+headset-mic ports).

Fixes: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/1028