Introduce a new component for MarkerShape and use it in SeriesPoint

[jleibs]

What

• Add new MarkerShape component
• Register a component-editor for it
• Use it in PointVisualizerSystem / TimeSeries space-view
• Bump up the radius for the point visualizer system

TODO:

• Store non-deterministically returns ComponentNotFound for new MarkerShape #5005

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

• PR Build Summary
• Docs preview
• Examples preview
• Recent benchmark results
• Wasm size tracking

[emilk]

Is "marker" the standard word for this?

[jleibs]

Is "marker" the standard word for this?

https://matplotlib.org/stable/api/markers_api.html
https://seaborn.pydata.org/tutorial/properties.html#marker
https://observablehq.com/plot/features/markers