List ad sets

Ad sets (Google ad groups) synced for the connection, optionally filtered by platform and campaignId. Reads the ad_sets table directly, independent of the ads rollup GET /v1/ads/tree uses, so a newly created standalone ad group with no ad yet (POST /v1/ads/ad-sets, Google only) is visible here even though it is invisible in the tree until an ad joins it via adSetId on POST /v1/ads/create. Returns at most 500 rows, newest first.