Output errors from nomad validate in line number:column: message form

### Proposal

Current output from nomad validate is rather for humans:

```
$ nomad validate /tmp/file.nomad
Driver configuration not validated since connection to Nomad agent couldn't be established.

Job validation errors:
2 errors occurred:
* Invalid job type: "sfdsavice"
* Task group cache validation failed: 2 errors occurred:
* Job type "sfdsavice" does not allow update block
* Job type "sfdsavice" does not allow migrate block
```

Please standardize output from nomad validate to something that can be parsable by machine. At best, please follow the format from gcc: `{file}:{line}:{column}: {severity}: {message}`.

### Use-cases
I wanted to add automatic nomad validate to my IDE. However, I do not know to which line the errors refer to, so it's kind of confusing.

### Attempted Solutions

`nomad validate --help` does not mention anything useful.

Thanks for making Nomad!

Start at the nomad validate command and inspect how validation errors are currently rendered; use the reported gcc-style format as the acceptance target. Done means errors include file, line, column, severity, and message in machine-parseable output suitable for IDE integration.

Written by the indexing model from the issue text.