Manage RELEASE_ENVIRONMENT_API_TOKEN with Terraform
## Context
We are using the token ENVIRONMENT_API_TOKEN to to update the resource group `process_mode` used in the `deploy` job of the [release-environments pipeline](https://gitlab.com/gitlab-org/gitlab/-/blob/master/.gitlab/ci/release-environments.gitlab-ci.yml?ref_type=heads).
* https://internal.gitlab.com/handbook/engineering/infrastructure/engineering-productivity/rotating-credentials/#environment_api_token
* https://gitlab.com/gitlab-org/gitlab/-/blob/master/.gitlab/ci/release-environments/security.gitlab-ci.yml?ref_type=heads#L132
Managing it with Terraform means one less token to rotate each year.
## Exit Criteria
* [x] RELEASE_ENVIRONMENT_API_TOKEN is managed by TF in the repo `infra-mgmt`
* [ ] Review and update https://gitlab.com/gitlab-com/gl-infra/delivery/-/issues/20170+
issue