List custom connectors available in the organization

Returns one entry per plugin_name, combining plugin metadata, the latest non-deleted file version (by semver), the distinct connector class types from that version, the total deployment_count across all versions (from user_config, synchronous), and the configuration_count of services actively running a connector class from this plugin (from service_state, collected asynchronously every ~15 minutes). Optionally filtered to a single plugin via plugin_name.