Investigate and test sentry integration

Summary

Seems like Pages is not reporting any errors to Sentry at all https://sentry.gitlab.net/gitlab/gitlab-pages/.

• We ignore the error when initializing the error tracker in https://gitlab.com/gitlab-org/gitlab-pages/-/blob/master/main.go#L28 so we might be blindly assuming it’s working, when in fact is not.
• There is a way to deploy a local instance of Sentry for testing purposes and integrate with the GDK gitlab-development-kit#748 (closed)
• Consider implementing some sort of catch-all error reporting.
• Verify the DSN set in https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/blob/master/roles/gprd-base-fe-web-pages.json#L32 is correct