Check if DbType is required, since now we are introducing SqlDbType

Bloating a ParamDefinition/ColumnDefinition with fields not relevant for every database seems not to be the best approach here.

_Originally posted by @ayush3797 in https://github.com/Azure/data-api-builder/pull/2052#discussion_r1535448998_

Start by reviewing the ParamDefinition and ColumnDefinition models and how DbType and SqlDbType are used across database providers. Determine whether DbType is still required and how provider-specific fields should be represented without burdening unrelated databases. Done means the model design is agreed and the affected usage and tests reflect that decision.

Written by the indexing model from the issue text.