[EPIC] Change JsonSchemaPrimitive to a class

[VitaliiMaltsev]

Tell us about the problem you're trying to solve

According to conversation in #7859 it's needed to change JsonSchemaPrimitive from enum to class which allows more flexible specifications

[tuliren]

• This issue needs a design doc first. We need to fully understand its impact on the destination side.
• If the implementation does not break destinations, carry on according to the design doc.
• If the implementation does break destinations, we need to
  • Update the destinations first (probably in dbt) to be compatible with both the date + time format, as well as the date-only format first.
  • Then make the change on the source side.

[VitaliiMaltsev]

@tuliren @sherifnada created design doc https://docs.google.com/document/d/1MxVLBuN2xDye0IPKsCsp4L5HLU6JosnWRxp3kEekpgw/edit. Please review