do not pickle cached hash of arrays #3222

Job	Run time
Documentation	1m 20s
Mypy	1m 37s
Conda Examples	1m 41s
Tests for downstream project meshmode	49m 49s
Tests for downstream project mirgecom	19s
Conda Pytest	6m 35s
Tests for downstream project grudge	25m 47s
Pylint	1m 29s
Ruff	5s
Tests for downstream project arraycontext	2m 51s
Typos	10s
	1h 31m 43s

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