Concurrent E2E runs can collide when provisioning policies on HCP
Consul and HCP Vault. Namespace these by the test run name, as we do
for most everything else.
Use HCP Consul and HCP Vault for the Consul and Vault clusters used in E2E testing. This has the following benefits:
* Without the need to support mTLS bootstrapping for Consul and Vault, we can simplify the mTLS configuration by leaning on Terraform instead of janky bash shell scripting.
* Vault bootstrapping is no longer required, so we can eliminate even more janky shell scripting
* Our E2E exercises HCP, which is important to us as an organization
* With the reduction in configurability, we can simplify the Terraform configuration and drop the complicated `provision.sh`/`provision.ps1` scripts we were using previously. We can template Nomad configuration files and upload them with the `file` provisioner.
* Packer builds for Linux and Windows become much simpler.
tl;dr way less janky shell scripting!
