Raw images are exported at half resolution

### Current Implementation RAW images are initially debayered at half resolution. This is great for in-app previews because it greatly improves load times, preview performance and results in an overall lower memory footprint. Currently this half-size-debayer is cached as VLT16 and reused for the final output render pass. ### Proposed Solution When exporting at a resolution that is bigger than the half-size-debayer, the original raw image files need to be debayered again, at full resolution, before final scaling and output render pass. This can be achieved by spawning a background thread that debayers and caches full resolution VLT16 after finishing loading the preview. This will be implemented along with larger ImageLoader refactoring.