Fix the video attachments now fetch the URL once on appear and pause when swiping to another item in the gallery.

[sheep-q]

🔗 Issue Links

N/A

🎯 Goal

• In StreamVideoPlayer, the AVPlayer adjusts the URL multiple times unnecessarily, causing it to reset its state when navigating back.
• AVPlayer continues playing video and audio when swiping to another item.

📝 Summary

• AVPlayer should fetch the URL once on appear.
• AVPlayer should stop when swiping to other item.

🛠 Implementation

Provide a detailed description of the implementation and explain your decisions if you find them relevant.

🎨 Showcase

Add relevant screenshots and/or videos/gifs to easily see what this PR changes, if applicable.

Before	After
img	img

🧪 Manual Testing Notes

Explain how this change can be tested manually, if applicable.

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• Changelog is updated with new localization keys
• New code is covered by unit tests
• Documentation has been updated in the docs-content repo

[laevandus]

It use to resume playback, therefore we should keep the same behaviour.

if let avPlayer {
                avPlayer.play()
                return
            }

[laevandus]

Verified it manually and ran CI checks separately