Add overlays for free-floating anchors on hovered/selected vector layers

[seam0s-dev]

Support for overlays as requested in #2558.

[seam0s-dev]

Test cases:
free-floating anchors.graphite.txt

[Keavon]

!build

[github-actions]

📦 Build Complete for 96b5e17
https://5420499d.graphite.pages.dev

[seam0s-dev]

@0HyperCube Ready for review.

[0HyperCube]

Thanks for your work so far.

I'm not really sure of the choice of the ManipulatorGroup to represent a single unconnected point with no handles.

I would also request tests before merging.
I've not manually tested this either but presumably it works mostly OK?

[Keavon]

See Discord comments. Marking as draft for the moment. Please mark as ready for review again once solved. Thanks :)

[Keavon]

!build

[github-actions]

📦 Build Complete for 8202c48
https://9a90f752.graphite.pages.dev

[Keavon]

Could you please make it work so when hovering over a point, it shows the overlays for the layer geometry, as it also does when hovering over a segment or filled shape? It looks like clicking those points works, but they're invisible until you actually click because hovering doesn't show it.

I'm also observing a crash that is hard to reproduce. I'll keep trying to make it relicatable.

[seam0s-dev]

I didn't understand what you meant specifically. I assume you meant that when you hover over a free-floating point on a layer that every shape on that layer also gets outlined, correct? If so, that does seems to work on my test cases.

free_floating_points.mp4

[seam0s-dev]

Crash might be due to this but, I am still unable to pinpoint what exactly is wrong with it:
https://github.com/GraphiteEditor/Graphite/pull/2630/files/e4f13954625fa5e1a8b2212c7850d18c8cfafe8f#diff-fe4d6f56fa9e774229baedb49b94d4dad31de3cd659209a538af1326e565f8f2R452-R456