Base expression node types on `dataclasses` #675

Job	Run time
Mypy	22s
Ruff	7s
Pytest on Py3.8	28s
Pylint	52s
Pytest on Py3.9	38s
Documentation	38s
Tests for downstream project loopy	3m 43s
Pytest on Py3.x	34s
Tests for downstream project pytential	44m 42s
Tests for downstream project pytato	6m 4s
	58m 8s

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