Add in-memory cache for autoedit suggestion images

[umpox]

Description

This PR implements an in-memory cache for autoedit suggestion images using the AutoeditRequestID as the cache key. The cache prevents regenerating the same image for repeated requests, improving performance.

Changes

• Added Map to store generated images keyed by AutoeditRequestID
• Updated generateSuggestionAsImage function to check the cache first
• Added cache clearing functions for both individual images and the entire cache
• Updated all call sites to pass the requestId parameter when available
• Added tests for the caching functionality

Testing

Added tests that verify:

• Images are cached correctly when using the same requestId
• Cache is properly invalidated when clearing specific images

These tests verify both the caching functionality and cache invalidation works as expected.