[feat] add wrapper function get a challenge's participant's team ID

[vpchung]

Describe The Problem To Be Solved

Use case: for one of the steps of Orca, @jaymedina needs to get the ID of a challenge's registered participant team, e.g.

The current solution is to use the REST API:

>>> syn.restGET("/entity/syn51317219/challenge").get('participantTeamId')
'3493415'

This would be a nice feature to have in cnb-tools.