Move the transition map members of the test context to a dedicated
structure. Move the transition variant pre-condition prepare, action,
and post-condition checks to a separate function to reduce the
indentation level and allow skipping of transition variants.
In the action requirements, some pre-conditions are not applicable
depending on the state of other pre-conditions. There is no particular
order in the pre-conditions, so we have to check the N/A status
individually.
