add device<->host transfer mappers #1611

Job	Run time
Examples Conda Py3	1m 30s
Mypy	1m 28s
Tests for downstream project meshmode	11m 31s
Documentation	1m 36s
Tests for downstream project grudge	9m 33s
Pylint	1m 39s
Tests for downstream project mirgecom	3s
Pytest Conda Py3 Intel	1m 49s
Pytest Conda Py3 POCL	2m 11s
Tests for downstream project mirgecom_examples	3s
Ruff	5s
Typos	6s
	31m 34s

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