Fix text layout cache key for maxFontSizeMultiplier

[KirtiRamchandani]

Summary:

Text layout measurement cache keys currently consider fontSizeMultiplier and allowFontScaling, but omit maxFontSizeMultiplier. When that cap changes, Fabric can reuse a stale measurement even though the effective scaled font size may change.

This adds maxFontSizeMultiplier to the layout-wise text attribute equality and hash helpers, and covers the cache-key behavior with focused C++ tests.

Fixes #56921.

Changelog:

[GENERAL] [FIXED] - Include maxFontSizeMultiplier in Fabric text layout cache keys.

Test Plan:

• npx --yes clang-format --dry-run --Werror packages/react-native/ReactCommon/react/renderer/textlayoutmanager/tests/TextLayoutManagerTest.cpp
• git diff --check

I could not run the native gtest target locally from this sparse checkout; the patch adds focused coverage in the existing TextLayoutManagerTest.cpp file.

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