Add convenient method of creating per-mip views for storage images. #687

Job	Run time
Build windows-latest \|\| SHARED=OFF \|\| PLATFORM=SDL	15m 37s
Build windows-latest \|\| SHARED=OFF \|\| PLATFORM=libretro	15m 16s
Build windows-latest \|\| SHARED=ON \|\| PLATFORM=SDL	14m 46s
Build windows-latest \|\| SHARED=ON \|\| PLATFORM=libretro	14m 40s
Build ubuntu-latest \|\| SHARED=OFF \|\| PLATFORM=SDL	18m 16s
Build ubuntu-latest \|\| SHARED=OFF \|\| PLATFORM=libretro	17m 28s
Build ubuntu-latest \|\| SHARED=ON \|\| PLATFORM=SDL	17m 34s
Build ubuntu-latest \|\| SHARED=ON \|\| PLATFORM=libretro	15m 45s
	2h 9m 22s

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