Search latency metrics are only recorded for authenticated users, biasing our measurements

Created by: slimsag

Search latency metrics/pings are only recorded for authenticated users: https://sourcegraph.com/github.com/sourcegraph/sourcegraph@798597d731a2384c26760d8a2ea47a284786471d/-/blob/cmd/frontend/graphqlbackend/search_results.go#L640-649

This will bias our results towards more complex queries (it means we don't measure the average person stumbling across sourcegraph.com and entering some basic query).