need a `nomad-template` cli like `consul-template`

### Proposal
I think there should be a way to render the "template" from the `template` stanza of **Nomad** using the cmd line on the target machine.
This would be useful during debugging.
It would be fine if it was a command/subcommand of the nomad binary as well.

### Use-cases
I had the following `template` in a Nomad job:

```bash
SOME_VAR="-Xms[[ env "attr.memory.totalbytes" | parseUint | divide 1048576 | multiply 0.60 | minimum 15360 | printf "%.0f" ]]m ...
```

I was trying to get 60% of total memory and use the minimum of _**that**_ and 15GB.

This worked fine for smaller sized machines, where the 60% was less than 15360m

For a machine with large memory, it failed with:
```
Invalid initial heap size: -Xms%!f(int64=15360)m
```

The message is very cryptic and the only clue being the `%!f`.

_What made it work was making `15360` to `15360.0` for the subsequent "float print"._

I wish there was a Nomad way to test this, using a cli tool like `consul-template`.

Typically I test consul specific templates using `consul-template` to figure out their accuracy, especially around newlines and spaces, etc.

### Attempted Solutions
None

Start by reviewing the Nomad template stanza and the nomad binary's CLI entry points, then compare the requested workflow with consul-template. Done means users can render and inspect a Nomad template from the target machine through a documented command or subcommand, including output that helps diagnose formatting issues.

Written by the indexing model from the issue text.