Adds Terraform configuration with rotate root API permissions

[austingebauer]

Overview

This PR adds on #65 to give the provisioned credentials the API permissions and app role assignments needed for the rotate root feature.

Contributor Checklist

• Add relevant docs to upstream Vault repository, or sufficient reasoning why docs won’t be added yet
  • Vault docs will be added to note minimal permissions needed.
• Add output for any tests not ran in CI to the PR description (eg, acceptance tests)
  • N/A for acceptance tests. I manually tested this with in-progress rotate root code from @vinay-gopalan.
• Backwards compatible

[vinay-gopalan]

Works great and LGTM! Thanks for adding this, super helpful 🙏🏼