[http-client-python] pyproject.toml doesn't keep EngSys-specific configs on regen

The following EngSys-specific configs should be kept in pyproject.toml on regeneration:
- [tool.uv.sources]
- [dependency-groups]

Example in [[azure-keyvault-keys]](https://github.com/Azure/azure-sdk-for-python/blob/8df21a0057e7d772d81d408a1daa7fca9b0bb094/sdk/keyvault/azure-keyvault-keys/pyproject.toml#L50-L65).

A couple of blocks should be added under [here](https://github.com/microsoft/typespec/blob/ef17c95cb1dbb61084d81abd96723fe334e02e47/packages/http-client-python/generator/pygen/codegen/serializers/general_serializer.py#L70) for these fields.