optimize the performance

[LucasXu0]

Rendering Optimization

• Support rendering only the on-screen block components.
• Support rendering the selection area or the cursor within the block components, making the selection behavior more customizable.
• Reduce unnecessary builds for the selection area.

Calculation Optimization

• Cache the children of the node to prevent multiple calculations.
• Optimize the selection calculation to only involve the visible block components.

[codecov]

Codecov Report

Patch coverage: 76.87% and project coverage change: +0.65% 🎉

Comparison is base (ad55171) 79.87% compared to head (b2d0865) 80.52%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #442      +/-   ##
==========================================
+ Coverage   79.87%   80.52%   +0.65%     
==========================================
  Files         276      280       +4     
  Lines       11526    11302     -224     
==========================================
- Hits         9206     9101     -105     
+ Misses       2320     2201     -119     

Files Changed	Coverage Δ
...nent/service/renderer/block_component_context.dart	100.00% <ø> (ø)
...omponent/service/scroll/mobile_scroll_service.dart	0.00% <0.00%> (-78.38%)	⬇️
...or/editor_component/service/selection_service.dart	100.00% <ø> (ø)
lib/src/render/selection/selection_widget.dart	0.00% <ø> (-100.00%)	⬇️
...uts/command_shortcut_events/backspace_command.dart	84.90% <27.27%> (-15.10%)	⬇️
...rtcuts/command_shortcut_events/delete_command.dart	76.19% <27.27%> (-17.56%)	⬇️
...se_component/selection/selection_area_painter.dart	28.57% <28.57%> (ø)
...t/image_block_component/image_block_component.dart	57.73% <50.00%> (+1.41%)	⬆️
...component/service/ime/non_delta_input_service.dart	83.72% <50.00%> (-0.54%)	⬇️
...vider_block_component/divider_block_component.dart	63.63% <66.66%> (+0.73%)	⬆️
... and 35 more

... and 7 files with indirect coverage changes

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