fix(iOS): reuse prefetched images

[CHANDRAMOHANnegi]

Summary:

Fixes #28557.

iOS image prefetch stores decoded images using their original-size cache key. Later image requests often include concrete dimensions, producing a different cache key and causing the prefetched image to be downloaded again.

This change falls back to the original-size cache entry for sized requests and reports prefetched decoded images as available in memory through Image.queryCache().

Changelog:

[IOS] [FIXED] - Reuse prefetched images for subsequent sized image requests

Test Plan:

• git diff --check — passed.
• Tested with RNTester on an iPhone simulator running iOS 26.5.
• Opened Image → Image Loading Events.
• Verified Image.prefetch() completed successfully.
• Verified Image.queryCache() returned disk/memory.
• Verified the prefetched image loaded and rendered at the requested dimensions without unexpected stretching, cropping, or distortion.

Screenshot: