Add option to disable env var interpolation in configs #1169

Job	Run time
Run tests with coverage	3m 4s
Run linters (flake8)	1m 48s
Run tests with different pydantic versions	3m 57s
Run tests (3.8)	2m 10s
Run linters (pydocstyle)	1m 44s
Run tests on legacy versions (3.7)	2m 17s
Run tests (3.9)	2m 7s
Run linters (mypy)	1m 53s
Run tests (3.10)	2m 10s
Run linters (pylint)	1m 48s
Run tests (3.11)	2m 5s
Run tests (3.12)	2m 15s
Run tests (3.13)	2m 8s
	29m 26s

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