Expose run name in dist/spmd components

[clumsy]

Description

The experiment name is currently exposed in dist/spmd components via TORCHX_TRACKING_EXPERIMENT_NAME.
But we don't have an env variable for run name.

Motivation/Background

This is very convenient to control e.g. MLflow client's experiment name via env variables via --name myexp/myrun.
TORCHX_JOB_ID is by definition unique and when we need to restart training for the same MLflow run, we would like to retain the previous run name.

Detailed Proposal

Set TORCHX_TRACKING_RUN_NAME in dist/spmd components similar to TORCHX_TRACKING_EXPERIMENT_NAME

Alternatives

Using TORCHX_JOB_ID won't help as it's unique by definition, but need to continue a run

Additional context/links

N/A