WGPU: Create cube textures with one layer per face #272

Job	Run time
build (windows, x86_64, msvc, Debug)	1m 5s
build (windows, x86_64, msvc, Release)	1m 52s
build (windows, aarch64, msvc, Debug)	1m 51s
build (windows, aarch64, msvc, Release)	2m 7s
build (linux, x86_64, gcc, Debug)	34s
build (linux, x86_64, gcc, Release)	36s
build (linux, x86_64, clang, Debug)	54s
build (linux, x86_64, clang, Release)	58s
build (linux, aarch64, gcc, Debug)	1m 17s
build (linux, aarch64, gcc, Release)	1m 23s
build (linux, aarch64, clang, Debug)	1m 10s
build (linux, aarch64, clang, Release)	1m 12s
build (macos, aarch64, clang, Debug)	57s
build (macos, aarch64, clang, Release)	1m 11s
	17m 7s

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