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.
This changeset stages upcoming E2E provisioning improvements work. It splits
the existing shared configuration directory into 3 profiles:
* "full-cluster": the set of configurations currently in use
* "dev-cluster": a simplified set of mostly existing configurations that
weren't in use.
* "custom": an empty profile for developers to keep non-standard
configurations during complex feature development.
The tooling to switch between profiles will be in a later changeset.
Also drops some unused configuration knobs from the provisioning scripts to
make the next stage of work easier.