[New Feature]: Stage-In Task without CWL

[LucaCinquini]

This task is analogous to Task #220 but without the using of CWL. In other words, the "cwl_task" that would invoke the "stage-in" CWL needs to be replaced with a "stage_in_task" which is also an instance of SpsKubernetesPodOperator, but invokes the Docker container: ghcr.io/unity-sds/unity-data-services:8.0.0 directly, passing all the proper parameters. The functionality of the DAG will be the same.