[FR] `--experiment` to support multiple experiment selection

[gunsodo]

As the issue name suggests, currently the user can choose to synchronizing either one specific experiment or all experiments. It would be nice to support multiple experiment selection.

An example usage could be

aimlflow sync --mlflow-tracking-uri={mlflow_uri} --aim-repo={aim_repo_path} --experiment=3,6,7

which synchronizes only three experiments.

I am also willing to submit a PR if allowed.