[charts-pro] Improve Sankey node label handling

[JCQuintas]

Fixes https://github.com/mui/mui-x/issues/20076

[mui-bot]

Deploy preview: https://deploy-preview-20191--material-ui-x.netlify.app/

Updated pages:

• docs/data/charts/sankey/sankey.md

Bundle size report

Bundle size will be reported once CircleCI build #695292 finishes.

Generated by :no_entry_sign: dangerJS against a6bb93fbaddcd86aa1cc1da8fa5424b4d5501ad5

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #20191 will degrade performances by 14.13%

_{Comparing JCQuintas:sankey-node-text (f8b4a73) with master (81ae8b1)[^unexpected-base]} [^unexpected-base]: No successful run was found on master (3914ec5) during the generation of this report, so 81ae8b1 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report.

Summary

❌ 3 regressions
✅ 10 untouched

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Change
❌	Simulation	SankeyChart with big data amount	115.1 ms	134 ms	-14.13%
❌	Simulation	ScatterChartPro with big data amount and zoomed in (single renderer)	65 ms	71.5 ms	-9.13%
❌	Simulation	ScatterChartPro with big data amount and zoomed in (batch renderer)	65.6 ms	72.1 ms	-9.06%

[github-actions[bot]]

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[github-actions[bot]]

This pull request has conflicts, please resolve those before we can evaluate the pull request.