Add simple terrain implementation #262

Job	Run time
build (stable, windows-latest)	4m 33s
build (stable, ubuntu-latest)	2m 49s
build (nightly, ubuntu-latest)	2m 37s
build (nightly, windows-latest)	4m 37s
build (nightly, macos-latest)	2m 2s
build (stable, macos-latest)	2m 21s
	18m 59s

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