Add a way to template nomad nodes (similar to consul nodes).

### Feature Request

Add a way to enumerate over nomad nodes (and fetch the node data like ip, etc) similar to how we do for consul - https://github.com/hashicorp/consul-template/blob/main/docs/templating-language.md#nodes

This will enhance nomad service discovery story.

### Use case
If we know which nodes nomad runs on can open up possibilities to connect to outside applications with known ports.

Start with the Consul templating-language nodes documentation linked in the issue and compare its behavior with the repository's existing Consul node support. Trace the relevant Go template entry points and tests, then define done as being able to enumerate Nomad nodes and retrieve node data such as IP addresses for service discovery.

Written by the indexing model from the issue text.