Remove the leftover geometry shader scaffolding

Nothing has generated or used a geometry shader since the GS paths were removed
- GeometryShaderGenerator is gone, and ShaderWriter's BeginGSMain/EndGSMain had
no callers at all. Removes ShaderStage::Geometry and everything hanging off it:
the GS preambles and GSMain helpers in ShaderWriter, the stage mappings in all
three thin3d backends, the D3D11 geometry shader plumbing (curGS_, the pipeline
and module members, gs_4_0 compilation), CreateGeometryShaderD3D11, the unused
PipelineFlags::USES_GEOMETRY_SHADER and PipelineManagerVulkan's
UsesGeometryShader().

Also stop enabling the Vulkan geometryShader device feature, since we no longer
have any use for it.

Kept on purpose: the device feature is still listed in the feature dumps (like
other capabilities we don't use), and the Vulkan shader cache header keeps its
now-always-zero geometry shader count so the on-disk format stays compatible.

GPU/D3D11/D3D11Util.cpp

@@ -113,20 +113,3 @@ HRESULT CreateComputeShaderD3D11(ID3D11Device *device, const char *code, size_t
 
 	return device->CreateComputeShader(byteCode.data(), byteCode.size(), nullptr, ppComputeShader);
 }
-
-HRESULT CreateGeometryShaderD3D11(ID3D11Device *device, const char *code, size_t codeSize, D3D_FEATURE_LEVEL featureLevel, UINT flags, ID3D11GeometryShader **ppGeometryShader) {
-	if (ppGeometryShader)
-		*ppGeometryShader = nullptr;
-	if (featureLevel <= D3D_FEATURE_LEVEL_9_3)
-		return S_FALSE;
-	std::string errorMessage;
-	std::vector<uint8_t> byteCode = CompileShaderToBytecodeD3D11(code, codeSize, "gs_5_0", flags, &errorMessage);
-	if (byteCode.empty()) {
-		if (!errorMessage.empty()) {
-			ERROR_LOG(Log::G3D, "%s", errorMessage.c_str());
-		}
-		return S_FALSE;
-	}
-
-	return device->CreateGeometryShader(byteCode.data(), byteCode.size(), nullptr, ppGeometryShader);
-}

GPU/D3D11/D3D11Util.h

@@ -78,7 +78,6 @@ std::vector<uint8_t> CompileShaderToBytecodeD3D11(const char *code, size_t codeS
 HRESULT CreateVertexShaderD3D11(ID3D11Device *device, const char *code, size_t codeSize, std::vector<uint8_t> *byteCodeOut, D3D_FEATURE_LEVEL featureLevel, UINT flags, ID3D11VertexShader **);
 HRESULT CreatePixelShaderD3D11(ID3D11Device *device, const char *code, size_t codeSize, D3D_FEATURE_LEVEL featureLevel, UINT flags, ID3D11PixelShader **);
 HRESULT CreateComputeShaderD3D11(ID3D11Device *device, const char *code, size_t codeSize, D3D_FEATURE_LEVEL featureLevel, UINT flags, ID3D11ComputeShader **);
-HRESULT CreateGeometryShaderD3D11(ID3D11Device *device, const char *code, size_t codeSize, D3D_FEATURE_LEVEL featureLevel, UINT flags, ID3D11GeometryShader **);
 
 #define ASSERT_SUCCESS(x) \
 	if (!SUCCEEDED((x))) \

GPU/Vulkan/PipelineManagerVulkan.h

@@ -37,7 +37,6 @@ class VulkanRenderManager;
 class VulkanContext;
 class VulkanVertexShader;
 class VulkanFragmentShader;
-class VulkanGeometryShader;
 class ShaderManagerVulkan;
 class DrawEngineCommon;
 
@@ -73,7 +72,6 @@ struct VulkanPipeline {
 
 	bool UsesBlendConstant() const { return (pipelineFlags & PipelineFlags::USES_BLEND_CONSTANT) != 0; }
 	bool UsesDepthStencil() const { return (pipelineFlags & PipelineFlags::USES_DEPTH_STENCIL) != 0; }
-	bool UsesGeometryShader() const { return (pipelineFlags & PipelineFlags::USES_GEOMETRY_SHADER) != 0; }
 	bool UsesDiscard() const { return (pipelineFlags & PipelineFlags::USES_DISCARD) != 0; }
 	bool UsesFlatShading() const { return (pipelineFlags & PipelineFlags::USES_FLAT_SHADING) != 0; }
 

GPU/Vulkan/ShaderManagerVulkan.cpp

@@ -73,7 +73,6 @@ static Promise<VkShaderModule> *CompileShaderModuleAsync(VulkanContext *vulkan,
 				switch (stage) {
 				case VK_SHADER_STAGE_VERTEX_BIT: createTag = "game_vertex"; break;
 				case VK_SHADER_STAGE_FRAGMENT_BIT: createTag = "game_fragment"; break;
-				case VK_SHADER_STAGE_GEOMETRY_BIT: createTag = "game_geometry"; break;
 				case VK_SHADER_STAGE_COMPUTE_BIT: createTag = "game_compute"; break;
 				default: break;
 				}
@@ -378,7 +377,7 @@ struct VulkanCacheHeader {
 	uint32_t detectFlags;
 	int numVertexShaders;
 	int numFragmentShaders;
-	int numGeometryShaders;
+	int unused_numGeometryShaders;  // Always 0, kept so the file format stays compatible.
 };
 
 bool ShaderManagerVulkan::LoadCacheFlags(FILE *f, DrawEngineVulkan *drawEngine) {
@@ -464,7 +463,7 @@ bool ShaderManagerVulkan::LoadCache(FILE *f) {
 		}
 	}
 
-	NOTICE_LOG(Log::G3D, "ShaderCache: Loaded %d vertex, %d fragment shaders and %d geometry shaders (failed %d)", header.numVertexShaders, header.numFragmentShaders, header.numGeometryShaders, failCount);
+	NOTICE_LOG(Log::G3D, "ShaderCache: Loaded %d vertex and %d fragment shaders (failed %d)", header.numVertexShaders, header.numFragmentShaders, failCount);
 	return true;
 }
 
@@ -476,7 +475,7 @@ void ShaderManagerVulkan::SaveCache(FILE *f, DrawEngineVulkan *drawEngine) {
 	header.detectFlags = 0;
 	header.numVertexShaders = (int)vsCache_.size();
 	header.numFragmentShaders = (int)fsCache_.size();
-	header.numGeometryShaders = 0;
+	header.unused_numGeometryShaders = 0;
 	bool writeFailed = fwrite(&header, sizeof(header), 1, f) != 1;
 	vsCache_.Iterate([&](const VShaderID &id, VulkanVertexShader *vs) {
 		writeFailed = writeFailed || fwrite(&id, sizeof(id), 1, f) != 1;