insights: Landing page pings backend work

Created by: CristinaBirkel

This issue is for any backend work related to landing page pings: https://github.com/sourcegraph/sourcegraph/issues/30608

• Adding total_insights to critical telemetry. https://github.com/sourcegraph/sourcegraph/pull/31270
• Hook up the new front end pings to get sent with the rest of the existing pings. https://github.com/sourcegraph/sourcegraph/pull/31048