insights: skip integration tests if DB unavailable in dev environments

Created by: slimsag

If a dev isn't running the code insights' TimescaleDB, and is trying to go test other code, it's nicer to skip these tests than to fail.

See https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/blob/internal/database/dbtesting/dbtesting.go#L73 for where we do this elsewhere.

Thanks @rvantonder for the idea: https://sourcegraph.slack.com/archives/C07KZF47K/p1611966174165500

Signed-off-by: Stephen Gutekanst [email protected]