In a fdl.Config for a dataclass, when accessing a field that uses a default_factory, populate a child Config (if not already present) wrapping the default_factory call, rather than raising a "Can't get default value for dataclass field ... since it uses a default_factory" error. #1810

	name: Python testing
	on:
	push:
	branches:
	- 'main'
	pull_request:
	branches:
	- 'main'
	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	python-version: ["3.8", "3.9", "3.10"]

	steps:
	- uses: actions/checkout@v3
	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v4
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install dependencies and package
	run: \|
	python -m pip install --upgrade pip
	pip install -e .[testing]
	- name: Test with pytest
	run: \|
	pytest --ignore=fiddle/_src/extensions/seqio_test.py fiddle

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