NOMAD_META_ environment variables

Is there a way to add `meta` arbitrary key-value pairs through environment variables?

Nomad can be used with `NOMAD_META_bar=foo`, but nomad-pack looks like ignores them

Start by tracing nomad-pack's environment-variable handling and compare it with the reported NOMAD_META_bar=foo example. Verify how arbitrary meta key-value pairs are parsed and passed through, then confirm that this variable produces the corresponding meta entry and that existing environment-variable behavior remains intact.

Written by the indexing model from the issue text.