Frontend chokes when loading region files with a large number of regions

After @pford fixed https://github.com/CARTAvis/carta-backend/issues/505, it looks like the issue now resides on the frontend. Loading a region file with ~3000 ellipses causes the frontend to completely choke. Memory usage keeps crawling up and CPU usage is around 100%