Change dates for visit, encounter, obs and encounter_diagnosis

[ReginaMerine]

When importing from MIMIC-IV, we were able to change the date of birth and death date with the anchor_age when creating patients in OpenMRS. However, the visit, encounter, obs and encounter_diagnosis entries include the MIMIC-IV dates without moving them to an approximate date.

Thus, any analysis needs to factor that if age is used for data related to obs or encounter.