trace, profiler, router: remove datadog
Created by: bobheadxi
This PR reverts datadog additions in a minimal manner, based on the decision to cease the datadog trial in https://github.com/sourcegraph/sourcegraph/issues/37568
Effectively reverts https://github.com/sourcegraph/sourcegraph/pull/31939, https://github.com/sourcegraph/sourcegraph/pull/32020, https://github.com/sourcegraph/sourcegraph/pull/33984, and friends.
Test plan
tests pass. also, it looks like traces are still being sent to Grafana Cloud (https://sourcegraph.grafana.net/goto/1HzKHcq7k?orgId=1), so this change should seamlessly just redirect users to Grafana Cloud instead of DataDog