[FIX] Cache maxDisplayRefreshRate on Android

[sbarrio]

What does this PR do?

Raised by: #1313

maxDisplayRefreshRate was not being cached on Android, which was effectively calling display.supportedModes on every frame callback.

With this change, the value is calculated once, stored on a cached shared value and reused for every subsequent frame callback.

Additional Notes

Thanks @ivan-moego to for raising.

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• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
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[Copilot]

Pull request overview

This PR addresses a performance issue on Android where Display.supportedModes was being queried on every frame callback when computing refresh-rate-normalized JS frame times. It introduces caching so the max display refresh rate is computed once and reused.

Changes:

• Cache the computed max display refresh rate in DdSdkImplementation to avoid repeated supportedModes calls on each frame.
• Standardize fallback refresh rate usage by using DEFAULT_REFRESH_HZ instead of a hardcoded 60.0.

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