[WebGPU] Code quality concerns raised for 191291: [WebGPU] Experimental prototype...

[WebGPU] Code quality concerns raised for 191291: [WebGPU] Experimental prototype for WebGPURenderPipeline and WebGPUSwapChain
https://bugs.webkit.org/show_bug.cgi?id=191383

Reviewed by Dean Jackson.

Covered by existing WebGPU tests introduced in original patch.

* Modules/webgpu/GPUDevice.h:
* Modules/webgpu/GPUPipelineStageDescriptor.h:
* Modules/webgpu/GPURenderPipelineDescriptor.h: Now a base struct with a guaranteed vertex stage member.
(): Refactored into enum class.
(WebCore::GPURenderPipelineDescriptor::GPURenderPipelineDescriptor): Removed in favor of init-list construction.
(WebCore::GPURenderPipelineDescriptor::primitiveTopology): Now a proper enum class member.
* Modules/webgpu/GPUShaderModule.h:
* Modules/webgpu/WebGPUDevice.cpp:
(WebCore::WebGPUDevice::createRenderPipeline const):
* Modules/webgpu/WebGPUShaderModule.h:
(WebCore::WebGPUShaderModule::module const):
* Modules/webgpu/WebGPUShaderStage.h: Replaced enum with constants to better reflect IDL.
* Modules/webgpu/cocoa/GPURenderPipeline.h:
* Modules/webgpu/cocoa/GPURenderPipelineMetal.mm:
(WebCore::setFunctionsForPipelineDescriptor):
(WebCore::GPURenderPipeline::create):
* Modules/webgpu/cocoa/GPUSwapChain.h:
* WebCore.xcodeproj/project.pbxproj: Removed GPUPipelineDescriptorBase.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@238208 268f45cc-cd09-0410-ab3c-d52691b4dbfc