The component loader is a more generic and extensible mechanism
of loading components; modules are one type of component...
The idea is to make scripts and config files also be components,
loaded by plugins that inherit WpComponentLoader
In case we have a multi-channel capture device and a mono client,
treat the MONO port as UNKNOWN and let it link with the first
port available on the device
Easy to test with arecord, which by default captures in MONO
+ expose the export transition in the session item class
+ make the export-related flags immutable
+ add an export error flag
+ update and improve documentation
+ replace calling execute_step(..., STEP_ERROR) with rollback
+ implement deactivate internally using rollback
This unifies deactivation steps, which are common between deactivate()
and calling execute_step() with WP_TRANSITION_STEP_ERROR at the
end of a failed activation transition.
