gpu: Skia Graphite build and feature flags

1. Add build and feature flags for Graphite, both disabled by default.
2. Add skia_use_metal buildflag for guarding metal code. This flag is
   only enabled with Graphite on developer builds.
3. Add SkiaGraphiteBackend to GpuPreferences, and parse its value from
   feature and command line flags. Also add a kNone option for Ganesh
   GrContextType for when Graphite is enabled.
4. Cleanup Chromium Skia BUILD.gn - more consistency between the config
   and sources in how we use conditionals. Ensure dawn and metal code is
   only built when Graphite is used, and other miscellaneous cleanup.
5. Remove Ganesh Dawn from Chromium including in blink over WebGPU
   command buffer, so both Dawn and Metal are only used with Graphite.

This doesn't yet rename the cc/viz pixel test enums - that will be a
separate followup change since it would otherwise add a dozen or two
more changed files to this CL.

Bug: 1429361
Change-Id: Ibf129727e03c303bfac85b98c111b08d880f408f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4404275
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Kyle Charbonneau <kylechar@chromium.org>
Reviewed-by: Kevin Lubick <kjlubick@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1128336}

• cc/paint/paint_image.cc[diff]
• cc/test/layer_tree_test.cc[diff]
• cc/test/pixel_test.cc[diff]
• components/viz/common/BUILD.gn[diff]
• components/viz/service/display/software_renderer.cc[diff]
• components/viz/service/display_embedder/skia_output_surface_dependency.h[diff]
• components/viz/service/display_embedder/skia_output_surface_impl.cc[diff]
• components/viz/service/display_embedder/skia_output_surface_impl_on_gpu.cc[diff]
• components/viz/service/display_embedder/skia_output_surface_impl_on_gpu.h[diff]
• components/viz/service/gl/gpu_service_impl.cc[diff]
• components/viz/service/gl/gpu_service_impl.h[diff]
• components/viz/test/BUILD.gn[diff]
• components/viz/viz.gni[diff]
• content/browser/gpu/compositor_util.cc[diff]
• gpu/command_buffer/service/BUILD.gn[diff]
• gpu/command_buffer/service/raster_decoder.cc[diff]
• gpu/command_buffer/service/service_utils.cc[diff]
• gpu/command_buffer/service/service_utils.h[diff]
• gpu/command_buffer/service/shared_context_state.cc[diff]
• gpu/command_buffer/service/shared_context_state.h[diff]
• gpu/command_buffer/service/shared_image/iosurface_image_backing.mm[diff]
• gpu/command_buffer/service/skia_utils.cc[diff]
• gpu/config/gpu_blocklist.cc[diff]
• gpu/config/gpu_blocklist_unittest.cc[diff]
• gpu/config/gpu_feature_type.h[diff]
• gpu/config/gpu_finch_features.cc[diff]
• gpu/config/gpu_finch_features.h[diff]
• gpu/config/gpu_info_collector.cc[diff]
• gpu/config/gpu_preferences.h[diff]
• gpu/config/gpu_switches.cc[diff]
• gpu/config/gpu_switches.h[diff]
• gpu/config/gpu_util.cc[diff]
• gpu/ipc/common/gpu_preferences.mojom[diff]
• gpu/ipc/common/gpu_preferences_mojom_traits.h[diff]
• gpu/ipc/service/gpu_channel_manager.h[diff]
• gpu/skia_bindings/BUILD.gn[diff]
• gpu/skia_bindings/grcontext_for_webgpu_interface.cc[Deleted - diff]
• gpu/skia_bindings/grcontext_for_webgpu_interface.h[Deleted - diff]
• services/viz/public/cpp/gpu/context_provider_command_buffer.cc[diff]
• services/viz/public/cpp/gpu/context_provider_command_buffer.h[diff]
• skia/BUILD.gn[diff]
• skia/features.gni[diff]
• third_party/blink/renderer/platform/BUILD.gn[diff]