replace pyrsistent.PMap, immutables.Map, immutabledict with constantdict #3442

Job	Run time
Mypy	1m 27s
Ruff	7s
Conda Examples	1m 57s
Tests for downstream project arraycontext	2m 7s
Documentation	1m 32s
Tests for downstream project meshmode	2m 5s
Pylint	1m 50s
Tests for downstream project grudge	2m 5s
Conda Pytest (ubuntu-latest)	2m 5s
Tests for downstream project pytential	2m 4s
Conda Pytest (macos-latest)	2m 9s
Conda Pytest with Intel CL	2m 6s
Tests for downstream project pytato	2m 3s
Conda Pytest without arg check	2m 3s
Conda Pytest Twice (for cache behavior)	2m 6s
Typos	4s
Tests for downstream project Firedrake	1m 53s
Validate CITATION.cff	7s
	29m 50s

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