Fix leftover use of module-reserve-device's state property to fix device registration

Merged Fabian Vogt requested to merge fvogt/wireplumber:reservationfix into master

The move to the WpDbus API dropped the "state" property from the plugin, but left the property enum and use of it in alsa.lua. Remove the enum and port over the code in alsa.lua.

This caused reserve-device plugin is not connected to D-Bus, disabling device reservation because a nonexisting property is nil and does not match connected.

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