feat: Add s3_outputs module to write shared values.

[eshiferax]

Create a new module s3_outputs and adding it to all root modules (controplane_rift, dataplane_rift, emr, databricks, dataplane_rift_with_emr). The bucket policy allows the control-plane account read-only access.

When users terraform apply the root modules, the outputs are written in a json file (outputs.json) to this bucket. Control plane can then retrieve these values.

Testing

Tested with controlplane_rift module. After terraform apply:

➜  aws-vault exec <controlplane> -- aws s3 ls s3://<clustername>-tecton-outputs
2025-06-09 09:37:09        220 outputs.json

➜  aws-vault exec <controlplane> -- aws s3 cp s3://<clustername>-tecton-outputs/outputs.json .

➜  cat outputs.json | jq '.'
{
  "cross_account_external_id": "CXOIQ41YDHRF0K1H",
  "cross_account_role_arn": "arn:aws:iam::<ACCOUNT_ID>:role/tecton-<clustername>-cross-account-role",
  "deployment_name": "<clustername>",
  "kms_key_arn": null,
  "region": "us-west-2"
}