Create new Mlflow run by default and introduce run_group

[chenmoneygithub]

What does this PR do?

Create new Mlflow run by default and introduce run_group. Currently the default behavior is to resume the Mlflow run by searching for existing run with the same name. As we discussed we should make the default behavior start a new run. Additionally to mirror the group in wandb, we are introducing the run_group tag.

What issue(s) does this change relate to?

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[mvpatel2000]

LGTM! It looks like your local linter may be applying a whole bunch of changes -- can we remove these? diff should be much smaller I think

[mvpatel2000]

LGTM! A minor nit for more helpful logs

[mvpatel2000]

more nits

[KuuCi]

@mvpatel2000 lgtm