Optimize overlays in CanvasKit (#47317)

Optimize overlays by detecting when Flutter-rendered content intersects
with platform views. Overlay canvases are only needed when the content
intersects, so by checking for this, we can optimize out most overlays.

## Pre-launch Checklist

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- [x] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I signed the [CLA].
- [x] All existing and new tests are passing.

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on [Discord].

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Author: harryterkelsen

ci/licenses_golden/licenses_flutter

@@ -38578,7 +38578,6 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/canvaskit_canvas.da
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/display_canvas_factory.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/embedded_views_diff.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/fonts.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/image.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart + ../../../flutter/LICENSE
@@ -38592,6 +38591,7 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/multi_surface_raste
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/n_way_canvas.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/native_memory.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/offscreen_canvas_rasterizer.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/overlay_scene_optimizer.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/path_metrics.dart + ../../../flutter/LICENSE
@@ -41435,7 +41435,6 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/canvaskit_canvas.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/display_canvas_factory.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart
-FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/embedded_views_diff.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/fonts.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/image.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart
@@ -41449,6 +41448,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/multi_surface_rasteri
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/n_way_canvas.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/native_memory.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/offscreen_canvas_rasterizer.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/overlay_scene_optimizer.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/path.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/canvaskit/path_metrics.dart

lib/web_ui/lib/src/engine.dart

@@ -25,7 +25,6 @@ export 'engine/canvaskit/canvaskit_canvas.dart';
 export 'engine/canvaskit/color_filter.dart';
 export 'engine/canvaskit/display_canvas_factory.dart';
 export 'engine/canvaskit/embedded_views.dart';
-export 'engine/canvaskit/embedded_views_diff.dart';
 export 'engine/canvaskit/fonts.dart';
 export 'engine/canvaskit/image.dart';
 export 'engine/canvaskit/image_filter.dart';
@@ -39,6 +38,7 @@ export 'engine/canvaskit/multi_surface_rasterizer.dart';
 export 'engine/canvaskit/n_way_canvas.dart';
 export 'engine/canvaskit/native_memory.dart';
 export 'engine/canvaskit/offscreen_canvas_rasterizer.dart';
+export 'engine/canvaskit/overlay_scene_optimizer.dart';
 export 'engine/canvaskit/painting.dart';
 export 'engine/canvaskit/path.dart';
 export 'engine/canvaskit/path_metrics.dart';