Fix text layout cache key for maxFontSizeMultiplier (#56960)

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 https://github.com/facebook/react-native/issues/56921.

## Changelog:

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

Pull Request resolved: https://github.com/facebook/react-native/pull/56960

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.

Reviewed By: sammy-SC

Differential Revision: D106362229

Pulled By: javache

fbshipit-source-id: 8977afe60b497344713af437eec48d5340eaed6c