Use common observation utility functions. #9406

Job	Run time
benchmark (e10_drive)	3m 28s
examples-rl (e10_drive)	5m 20s
benchmark (e11_platoon)	2m 25s
base-tests (./cli)	2m 45s
examples-rl (e11_platoon)	2m 58s
base-tests (./envision)	3m 29s
base-tests (./smarts/core --nb-exec-timeout 65536 --ignore=./smarts/core/tests/test_notebook.py)	23m 11s
base-tests (./smarts/env --ignore=./smarts/env/tests/test_rllib_hiway_env.py)	4m 40s
base-tests (./smarts/env/tests/test_rllib_hiway_env.py)	3m 2s
base-tests (./smarts/sstudio)	2m 57s
base-tests (./smarts/ray)	4m 19s
base-tests (./examples/tests/test_examples.py)	5m 44s
	1h 4m 18s

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