[Maps] scale marker size by area

[nreese]

Fixes #131698

This PR updates the maplibre style expression to interpolate over the square root of value instead of value to avoid distorting proportions when styling marker areas.

This has the visual effect of making markers for smaller values larger by reducing the interpolation range.
For example, with a marker size range of [8, 32] and a data range of [0, 100]

• before the change, the interpolation stops would be 0, 8, 100, 32,
• after the change, the interpolation stops are 1, 8, 10.04987562112089, 32. Notice how the data range was reduced from [0, 100] to [1, 10.04987562112089] (there is also a value shift to avoid taking square root of zero or a negative number).

Before

After

Notice the larger circles for the values in Alaska

[nreese]

@elasticmachine merge upstream

[kibana-ci]

💚 Build Succeeded

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• Commit: 27dbf3c
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Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
maps	792	793	+1

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
maps	2.5MB	2.5MB	-153.0B

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[jsanz]

This is looking great, showing side to side between this PR on the left and current view (8.2.0) on the right, as in the PR description, the size of the smaller points improves.

I wonder, and it would go a follow up PR for sure, if we could improve the way the symbol size is communicated in the legend so users understand better the mapping between values and symbol size.

This wikipedia example shows a very classic way to display point sizes, but even just showing the actual max/min point sizes in the current legend, maybe adding a midpoint, could already improve a lot. @gvnmagni what do you think?

[gvnmagni]

This wikipedia example shows a very classic way to display point sizes, but even just showing the actual max/min point sizes in the current legend, maybe adding a midpoint, could already improve a lot. @gvnmagni what do you think?

I love that idea Jorge, it would help a lot our users understanding the proportion and it will guide then in reading values even without hovering with the cursor 👍

[jsanz]

Tested locally on Chrome