perf(ui): rendering optimizations

[psychedelicious]

Summary

Handful of optimizations implemented while attempting to get a performant full canvas preview (unfortunately unsuccessful).

• Do not rely on internal Konva API for layer preview canvas (indirectly addresses #6950)
• Track whether layers intersect the bbox
• Track whether layers are on-screen
• Disable Konva's "perfect draw" for all shapes
• Hide layers when they are both off-screen and not the selected layer
• Throttle opacity and compositing fill rendering to 100ms
• Reduce compositing rect rendering to minimum

Related Issues / Discussions

Closes #6950

QA Instructions

Have a play, should be no change to behaviour. I think I can feel it is a bit snappier but could be wishful thinking.

Merge Plan

n/a

Checklist

• [x] The PR has a short but descriptive title, suitable for a changelog
• [ ] Tests added / updated (if applicable)
• [ ] Documentation added / updated (if applicable)