chore: [DHIS2-21515] Improve performance for large option sets in SingleSelectField

[henrikmv]

DHIS2-21515

This change introduces incremental client-side rendering using the onEndReached prop already exposed by @dhis2/ui's SimpleSingleSelect. Options remain fully in-memory (no server-side change), but only a window is mounted at a time:

• Activates only when filteredOptions.length > 200; smaller option sets render as before.
• Renders the first 100 options initially; onEndReached appends another 100 as the user scrolls.
• Window resets to the first 100 on every filter change so search results always start from the top.
• Selected value is still resolved against the full options array, so it displays correctly even when outside the rendered window.

[github-actions]

🚀 Deployed on https://deploy-preview-4572.capture.netlify.dhis2.org

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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