Make GH actions strategy more concise #82

Job	Run time
build	1m 40s
lint	1m 28s
unit-tests (16, ubuntu)	1m 29s
unit-tests (16, macos)	2m 15s
unit-tests (16, windows)	6m 39s
unit-tests (18, ubuntu)	1m 32s
unit-tests (18, macos)	3m 4s
unit-tests (18, windows)	5m 7s
integration-tests (18, ubuntu, chromium)	3m 41s
integration-tests (18, ubuntu, firefox)	3m 42s
integration-tests (18, windows, chromium)	8m 7s
integration-tests (18, windows, firefox)	7m 17s
	46m 1s

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