fix: detect and mask out photo library and user photos

[ioannisj]

💡 Motivation and Context

Best effort to detect and mask any UIImage which belongs to the user's photo library

We also try to detect system image pickers (and other remote views) and mask those out as well

Docs: PostHog/posthog.com#9968

Before

After

💚 How did you test it?

Locally in UIKit sample project with an image picker view

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.