Remove long-deprecated special-casing of meshmode DOFArrays #1814

Job	Run time
Typos	6s
Ruff	4s
basedpyright	1m 39s
Documentation	1m 40s
Tests for downstream project meshmode	10m 54s
Tests for downstream project grudge	9m 42s
Examples Conda Py3	1m 10s
Mypy	1m 34s
Tests for downstream project mirgecom	5s
Pytest Conda Py3 Intel	1m 51s
Tests for downstream project mirgecom_examples	4s
Pytest Conda Py3 POCL	2m 8s
	30m 57s

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