[EPIC] Create purely pythonic `nv_ingest_common` module

There is currently duplicative code in both nv_ingest and nv_ingest_client. The duplicative code ranges from Pydantic schemas that are needed in both modules to utility functions needed in both locations. The goal of this Epic is to setup a nv_ingest_common module that takes the duplicative code from each independent module and places it in a common/shared location.

Furthermore this module should be a lite and purely python as possible. This module should be written in a fashion where other libraries or runtimes can import it and use in a fashion similar to nv_ingest_runtime. This of course means that nv_ingest_runtime will need some refactoring to work with code that is moved to this common module.

This Epic can be broken down into the follows issues.