Add visual test for ScatterRegionLayerArtist #579

Job	Run time
initial_checks / Load tox environments	5s
initial_checks / codestyle (ubuntu-latest)	33s
tests / Load tox environments	7s
tests / py38-test-lts-all (ubuntu-latest)	1m 23s
tests / py39-test (ubuntu-latest)	1m 28s
tests / py310-test-all (ubuntu-latest)	1m 47s
tests / py311-test (ubuntu-latest)	1m 21s
tests / py311-test-all (ubuntu-latest)	2m 23s
tests / py38-docs (ubuntu-latest)	4m 1s
tests / py311-docs (macos-latest)	5m 12s
tests / py38-test-all (macos-latest)	1m 58s
tests / py39-test (macos-latest)	1m 51s
tests / py310-test-all (macos-latest)	4m 31s
tests / py311-test (macos-latest)	1m 46s
tests / py38-test (windows-latest)	3m 20s
tests / py310-test (windows-latest)	2m 54s
tests / py310-test-dev-all (ubuntu-latest)	1m 44s
tests / py311-test-dev (ubuntu-latest)	2m 3s
publish / Build source and wheel distribution	3m 2s
	41m 29s

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