Use one environment.yml for all platforms #278

Job	Run time
continuous-integration / build-macos	4m 25s
continuous-integration / build-windows (Release, windows-2019)	3m 50s
continuous-integration / build-windows (Release, windows-latest)	3m 54s
continuous-integration / build-linux (Debug, ubuntu-latest)	5m 32s
continuous-integration / build-linux (Debug, ubuntu-20.04)	4m 38s
continuous-integration / build-linux (Release, ubuntu-latest)	2m 2s
continuous-integration / build-linux (Release, ubuntu-20.04)	2m 13s
continuous-integration / test-windows	0s
continuous-integration / test-macos	4m 29s
continuous-integration / test-linux (Debug, ubuntu-20.04, true)	2m 57s
continuous-integration / test-linux (Release, ubuntu-latest, true)	2m 53s
continuous-integration / test-linux (Release, ubuntu-20.04, true)	2m 19s
continuous-integration / test-linux (Debug, ubuntu-latest, false, ON)	6m 34s
continuous-integration / draft-release	0s
	45m 46s

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