Adding field  in processing step to support aggregations at worker level
In https://github.com/huggingface/datasets-server/issues/734 and https://github.com/huggingface/datasets-server/issues/755 we need to create a new worker that will compute splits based on split names by config see comment https://github.com/huggingface/datasets-server/issues/755#issuecomment-1428236340 .
I added a new field on processing step so that we can define the aggregation level.
e.g: 
For /splits endpoint we will have two different responses based on query params:
-` ?dataset=...config=...` Respond with processing steps `[/split-names-from-streaming, /split-names-from-dataset-info] `
- `?dataset= ` Respond with two new processing steps` [/dataset-split-names-from-streaming, /dataset-split-names-from-dataset-info] `

`/dataset-split-names-from-streaming` depends on `/split-names-from-streaming`
`/split-names-from-streaming` input type is `config` and in db its granularity is dataset and config but we only need one record in the db for `/dataset-split-names-from-streaming` that will summarize the previous entries.
For the specific case of /dataset-split-names-from-streaming new worker, there will exist a new Job after /split-names-from-streaming but there will exist only 1 record for  /dataset-split-names-from-streaming that will be updated N times.
If processing step is "config" but aggregation level is "dataset" one Job in the Queue per config but the result will be only one record in Cache.

Adding field  in processing step to support aggregations at worker level: In https://github.com/huggingface/datasets-server/issues/734 and https://github.com/huggingface/datasets-server/issues/755 we need to create a new worker that will compute splits based on split names by config see comment https://github.com/huggingface/datasets-server/issues/755#issuecomment-1428236340 .
I added a new field on processing step so that we can define the aggregation level.
e.g: 
For /splits endpoint we will have two different responses based on query params:
-` ?dataset=...config=...` Respond with processing steps `[/split-names-from-streaming, /split-names-from-dataset-info] `
- `?dataset= ` Respond with two new processing steps` [/dataset-split-names-from-streaming, /dataset-split-names-from-dataset-info] `

`/dataset-split-names-from-streaming` depends on `/split-names-from-streaming`
`/split-names-from-streaming` input type is `config` and in db its granularity is dataset and config but we only need one record in the db for `/dataset-split-names-from-streaming` that will summarize the previous entries.
For the specific case of /dataset-split-names-from-streaming new worker, there will exist a new Job after /split-names-from-streaming but there will exist only 1 record for  /dataset-split-names-from-streaming that will be updated N times.
If processing step is "config" but aggregation level is "dataset" one Job in the Queue per config but the result will be only one record in Cache.
