Add Google Cloud Profiler support

We are investigating a high memory situation in gitlab#355460 (closed), which we cannot reproduce locally.

We should add cloud profiling support via labkit so that we can observe CPU and memory use in a live instance.

Steps

• Integrate with labkit monitoring
• Update gitlab-com settings to set GITLAB_CONTINUOUS_PROFILING on webservice
• Create team Access Request with roles/cloudprofiler.user for the gitlab-production gcp project Looks like we already have access.

Links

• https://gitlab.com/gitlab-org/labkit/-/blob/master/monitoring/doc.go