LazilyUnpickling{Dict,List}: add repr #3050

Job	Run time
Pylint	2m 12s
Conda Pytest (ubuntu-latest)	4m 6s
Conda Examples	2m 23s
Conda Pytest (macos-latest)	10m 46s
Documentation	2m 0s
Flake8	23s
Conda Pytest without arg check	4m 1s
Conda Pytest Twice (for cache behavior)	5m 10s
Tests for downstream project Firedrake	15m 46s
Tests for downstream project arraycontext	2m 41s
Mypy	1m 48s
Tests for downstream project meshmode	10m 47s
Conda Pytest with Intel CL	4m 11s
Tests for downstream project grudge	7m 18s
Tests for downstream project pytential	33m 24s
Tests for downstream project pytato	5m 16s
	1h 52m 12s

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