Add unique ingestion id for all batch ingestions

[zhilingc]

What this PR does / why we need it:
This is a split-off off #612 that introduces the model changes made in that PR in a more digestible chunk.

Adds a unique identifier for all discrete batch loads of data into feast for re-referencing the set of data later on.

Does this PR introduce a user-facing change?:

Adds dataset_id field into BQ

[zhilingc]

/test test-end-to-end

[zhilingc]

/test test-end-to-end-batch

[woop]

I am personally happy to merge this at any time. I'll leave it open for a little bit.

[ches]

Fine from me functionally. I have the exact same reaction as @woop on #612 (comment) – the name "dataset" feels off to me for this, and my first inclination was also ingestion_id.

[zhilingc]

@ches I just felt it was more intuitive to provide a dataset id over an ingestion id, and in the old PR I originally offered the functionality for the user to be able to set it, but it was punted to when we integrate these ids into batch retrieval. But i can't say i'm too opinionated about this. if you guys think it should be ingestion_id I'm happy to change it.

[woop]

@ches I just felt it was more intuitive to provide a dataset id over an ingestion id, and in the old PR I originally offered the functionality for the user to be able to set it, but it was punted to when we integrate these ids into batch retrieval. But i can't say i'm too opinionated about this. if you guys think it should be ingestion_id I'm happy to change it.

I think your previous concern was around the retrieval of statistics based on an ingestion filter being unintuitive? I can see that.

We are starting to overload this ingestion term as well, with IngestionJob in the Python SDK referring to the population jobs. There is a bit of disconnect between those two ingestion flows right now, but I do think they can be one flow (ingest, populate) in the future so keeping the names the same seems reasonable to me.

So anyway, my preference is ingestion_id, but I also do think dataset_id would work in some sense.

[zhilingc]

Renamed to ingestion_id and rebased on master.

[woop]

/lgtm

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