Pull `ingest_datetime` through to core

[krishyfishy]

Is your feature request related to a problem? Please describe.
The main goal here is to strengthen traceability between raw data, input layer, and core. If, for example, a payer sends info for a specific claim 6 months in a row, tables downstream of the input layer may not convey this info appropriately.

#1013 added file_date to core, improving traceability—but having both fields (file_date and ingest_datetime) would be helpful.

Describe the solution you'd like
Add ingest_datetime to core.medical_claim, core.pharmacy_claim, core.eligibility

Describe alternatives you've considered
Could consider implementing some sort of first ingested / last ingested, but an approach like this would allow for users to make use of flexibility in mapping fields to columns that already exist in the input layer and minimize changes to the data model

Additional context