feat(alerts): automatically generate a tamland alert for capacity planning forecast violations

At present, we need to manually open an issue when a violation is forecast in Tamland.

This change automatically opens an alert in https://gitlab.com/gitlab-com/gl-infra/capacity-planning tracker.

With the current configuration, the alert will not automatically create an incident, but remain only as an alert. An operator can manually create an "incident" from the alert.

Note that this alert will never page the oncall or be routed to pagerduty.

Additional notes:

1. Alerts will arrive in https://gitlab.com/gitlab-com/gl-infra/capacity-planning/-/alert_management
2. Token obtained from https://gitlab.com/gitlab-com/gl-infra/capacity-planning/-/settings/operations
3. The secret for integrating alert manager with GitLab has already been configured in https://ops.gitlab.net/gitlab-com/runbooks/-/settings/ci_cd