Pass urlPath to imageOptimization even if disabled

The imageOptimization takes a very long time for only a few images and I'd only like it to run on production, but I still need images to be prefixed with urlPath when they are not optimized and are given eleventyConfig.addPassthroughCopy if on development. This way, when the plugin doesn't optimize the images, their reference source still works in the rendered html files.

Start by locating the imageOptimization handling and the eleventyConfig.addPassthroughCopy path. Trace the disabled-optimization flow when urlPath is configured, then verify that development output references the prefixed, passthrough-copied images correctly in the rendered HTML.

Written by the indexing model from the issue text.