offload VQ image processing onto pooled worker threads & loading indicator

[rob2d]

For specific image textures in MVC2 and CVS2, vector quantization is used to compress and decompress parts of images. compressVqBuffer uses k-clustering and is suboptimal to offload onto the main thread -- can take up to 60 seconds depending on clients PC.

Similar to loading polygon and texture files, compression before export overall should take place in pool-able ClientWorker threads.

In addition to that, state management will be needed. It may be worth considering adding RTK Query to redux toolkit to manage async state. Otherwise, a variable and UI indicator for pending/rejected/success should be managed to show a loading spinner while a user exports these.

For the moment users use it without issue but this is essentially QOL as expanding support to other games will make the issue more noticeable. It will also be easier to parallelize operations for multi file support once this occurs on another thread with a proper dialog.