Based on feedback, reverted most group changes
* reverted all changes to group requirements to before this PR
* aside from impact on related_agent flag, and some "how to match on groups" clarifications, removed group query changes except to forbid anonymous groups as a filter option for agent parameter

Leaving prohibition of anonymous groups as a query parameter (and specificatoin that for an identified group specified
as a search parameter only the identifier is relevant) to avoid requiring LRS to search on a list of agents.