Provisions vault with the policies described in the Nomad Vault integration
guide, and drops a configuration file for Nomad vault server configuration
with its token. The vault root token is exposed to the E2E runner so that
tests can write additional policies to vault.
Adds a `nomad_acls` flag to our Terraform stack that bootstraps Nomad ACLs via
a `local-exec` provider. There's no way to set the `NOMAD_TOKEN` in the Nomad
TF provider if we're bootstrapping in the same Terraform stack, so instead of
using `resource.nomad_acl_token`, we also bootstrap a wide-open anonymous
policy. The resulting management token is exported as an environment var with
`$(terraform output environment)` and tests that want stricter ACLs will be
able to write them using that token.
This should also provide a basis to do similar work with Consul ACLs in the
future.
