Add `-m` flag to torchrun-hpc

[tbennun]

Like the Python executable and torchrun, the -m flag allows a CLI to call an installed Python module.

We should integrate the -m flag to torchrun-hpc by:

1. Adding a flag to the torchrun-hpc CLI: hpc_launcher/cli/torchrun_hpc.py
2. Enabling module execution in the torchrun-hpc trampoline: hpc_launcher/torch/torchrun_hpc_trampoline.py

We should also add a test.