fix(textblock): fix invalidation when font fallback asynchronously gets a new font

[ramezgerges]

GitHub Issue: closes #22625

PR Type:

What is the current behavior? 🤔

What is the new behavior? 🚀

PR Checklist ✅

Please check if your PR fulfills the following requirements:

• 📝 Commits must be following the Conventional Commits specification.
• 🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
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• ❗ Contains NO breaking changes

Other information ℹ️

[Copilot]

Pull request overview

This PR addresses a Skia TextBlock rendering issue where asynchronous font fallback resolution doesn’t trigger the necessary layout invalidation, leaving displayed glyphs stale until another UI interaction forces a refresh.

Changes:

• Update TextBlock’s UnicodeText.IFontCacheUpdateListener.Invalidate() to call InvalidateMeasure() so layout (and text shaping) is recomputed when fallback fonts become available.

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[ramezgerges]

There's supposed to already be a runtime test ("Check_FontFallback_Shaping2") for this but for some reason it's passing in CI before the fix. Locally, it (correctly) fails.

[unodevops]

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