vulkan: Fix crashes with bindless texture constant buffer handling

Previously, the code would unconditionally add a constant buffer descriptor
at index 0 whenever storage buffers were present, which could cause conflicts
and crashes. This change:

- Adds validation to check if constant buffer 0 already exists
- Only adds the descriptor if it's not already present
- Prevents potential descriptor conflicts in shaders

This should resolve crashes in Vulkan games related to invalid descriptor
layouts and resource binding conflicts.

src/video_core/renderer_vulkan/vk_pipeline_cache.cpp

@@ -768,13 +768,21 @@ std::unique_ptr<ComputePipeline> PipelineCache::CreateComputePipeline(
 
     auto program{TranslateProgram(pools.inst, pools.block, env, cfg, host_info)};
 
-    // Add support for bindless texture constant buffer
+    // Add support for bindless texture constant buffer only if needed
     if (program.info.storage_buffers_descriptors.size() > 0) {
+        // Check if a constant buffer at index 0 already exists
+        const bool has_cb0 = std::any_of(program.info.constant_buffer_descriptors.begin(),
+                                        program.info.constant_buffer_descriptors.end(),
+                                        [](const auto& cb) { return cb.index == 0; });
+
+        // Only add if not already present
+        if (!has_cb0) {
             Shader::ConstantBufferDescriptor desc;
             desc.index = 0;
             desc.count = 1;
             program.info.constant_buffer_descriptors.push_back(desc);
         }
+    }
 
     const std::vector<u32> code{EmitSPIRV(profile, program)};
     device.SaveShader(code);