ggml-backend : add GGML_BACKEND_DEVICE_TYPE_IGPU device type (#15797) #13

Job	Run time
ubuntu-22-cpu (x64, ubuntu-22.04)	3m 52s
macOS-arm64	2m 44s
macOS-x64	9m 7s
ubuntu-22-vulkan	7m 21s
windows (opencl-adreno, arm64, -G "Ninja Multi-Config" -D CMAKE_TOOLCHAIN_FILE=cmake/arm64-window...	1m 42s
windows-cpu (arm64)	3m 0s
windows-cuda (12.4)	49m 3s
windows-cpu (x64)	5m 13s
windows (vulkan, x64, -DGGML_VULKAN=ON, ggml-vulkan)	4m 19s
windows-sycl	13m 57s
ios-xcode-build	20m 33s
windows-hip (radeon, gfx1100;gfx1101;gfx1102;gfx1030;gfx1031;gfx1032)	50m 3s
release	1m 37s
	2h 52m 31s

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