Migrate from simple-parsing to pydantic for argument parsing

[deepakn97]

Describe the feature

We want better configuration management and argument parsing for CLI and the API. To support the development, drop support for simple-parsing in favor of pydantic.

Potential Solutions

1. Use Pydantic for creating configuration classes.
2. Decouple API and CLI fields in data classes and configuration.
3. Migrate the CLI to use Pydantic and Pydantic Argparse.