Orchestrate reading editor bounding boxes across editor renderings

[alexdima]

Fixes #290537

[Copilot]

Pull request overview

This PR refactors the editor rendering pipeline to introduce a coordinated pre-render phase where view parts can read layout-related information (like DOM bounding boxes) before any editor instance mutates the DOM, reducing redundant synchronous layouts across multiple editors. It leverages a new onBeforeRender hook on ViewPart and updates the native edit context to cache container bounds ahead of rendering selection and character bounds.

Changes:

• Introduced a ViewPart.onBeforeRender(viewportData) lifecycle hook and wired the View to call it for all view parts that need to render, before any text rendering occurs.
• Updated the coordinated rendering flow (ICoordinatedRendering, EditorRenderingCoordinator, and View._flushAccumulatedAndRenderNow) to compute and pass a shared ViewportData object explicitly between the pre-render and render phases.
• Modified NativeEditContext and content widgets to use onBeforeRender to cache editor container bounds and to avoid per-render getBoundingClientRect() calls that previously caused multiple synchronous layouts when many rich answers/code blocks are present.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/vs/editor/browser/viewParts/contentWidgets/contentWidgets.ts	Marks ViewContentWidgets.onBeforeRender as an override and forwards the new ViewportData to all content widgets so they can participate in the pre-render phase.
src/vs/editor/browser/view/viewPart.ts	Adds the ViewportData import and defines a default no-op onBeforeRender(viewportData) hook on ViewPart as the new pre-render extension point.
src/vs/editor/browser/view.ts	Refactors the render pipeline to return ViewportData from prepareRenderText, pass it into renderText, invoke onBeforeRender on view parts before text rendering, and updates ICoordinatedRendering / EditorRenderingCoordinator to orchestrate pre-render and render across multiple editors using this shared viewport data.
src/vs/editor/browser/controller/editContext/native/nativeEditContext.ts	Adds a cached _parentBounds updated in onBeforeRender, removes the onDidRender-based post-pass, and switches selection/control and character bounds calculations to use the cached bounds to avoid extra layout flushes while keeping them aligned with the current viewport.