fix: video thumbnail loading

[isekovanic]

🎯 Goal

This PR fixes video thumbnail loading logic so that it is consistent across video thumbnails and image attachments.

Additionally, it:

• Improves performance on Android by reducing the number of moving parts in the shimmering layer (same as we did for iOS)
• Introduces an orchestrator so that each shimmering view doesn't create its own ValueAnimator unnecessarily
• Makes sure offscreen views are not animating (they still stay registered though unless they actually unmount/detach)
• Fixes offline images with the new FastImage library in the sample app

🛠 Implementation details

🎨 UI Changes

iOS

Before	After

Android

Before	After

🧪 Testing

☑️ Checklist

• I have signed the Stream CLA (required)
• PR targets the develop branch
• Documentation is updated
• New code is tested in main example apps, including all possible scenarios
  • SampleApp iOS and Android
  • Expo iOS and Android

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
js_bundle_size	360 KB	360 KB	0 B	🟢