Refactor renderer RHI with WebGPU-style RenderPass management

[Copilot]

Introduces a RenderPass abstraction layer to route command buffers to different render passes (Opaque/Transparent/Offscreen) based on rendering state, enabling future WebGPU integration.

Changes

New RenderPass Infrastructure (src/renderer/render_pass.hpp/cpp)

• RenderPassType enum: kOpaque, kTransparent, kOffscreen
• TrRenderPass class wrapping GPURenderPassEncoder for command buffer management
• TrRenderPassCollection managing per-content-renderer passes

Command Buffer Routing (TrContentRenderer)

• determineRenderPassType() routes based on:
  • Non-default framebuffer binding → Offscreen
  • Blending enabled + draw call → Transparent
  • Default → Opaque
• State tracking for isBlendingEnabled_ and currentBoundFramebuffer_

Render Pass Execution

• onTransparentsRenderPass() executes transparent pass command buffers
• onOffscreenRenderPass() integrated with render pass collection
• onStartFrame() resets pass collection and state tracking

State Tracking in RHI (render_api_opengles.cpp)

• OnEnable/OnDisable track GL_BLEND state
• OnBindFramebuffer tracks current framebuffer binding

Usage

// Routing decision during execution
RenderPassType passType = contentRenderer->determineRenderPassType(commandBuffer);
auto* pass = renderPassCollection_.getOrCreatePass(passType);
pass->addCommandBuffer(commandBuffer);

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Original prompt

选择的分支它主要实现以下功能：重构 renderer 的 RHI，使用 WebGPU 作为 RHI 的具体实现，使得客户端提交的渲染指令我们可以自由的安排在不同的 RenderPass 中，如 OpaqueRenderPass/TransparentRenderPass/OffscreenRenderPass。

请基于目前已经实现的部分，继续实现：

1. 在 Renderer 中添加一个 RenderPass 的类，它内部基于 GPURenderPassEncoder 用于维护每个 Content Renderer 中的不同 RenderPass，比如 OpaqueRenderPass/TransparentRenderPass/OffscreenRenderPass
2. 在 TrContentRenderer::onCommandBufferRequestReceived 中，根据一些规则来添加对不同的 RenderPass 中，比如 framebuffer 如果不在当前 fbo 那么就添加到 offscreen renderpass，如果开启了 blending 那么就添加到 transparent renderpass 等
3. 在 TrContentRenderer 中，不同的 on*RenderPass 时，调用对应的 GPURenderPassEncoder 去执行 commandbuffer（但具体的执行逻辑是在 renderer/gles 中使用 GLES API 实现）

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