NOTE: This commit only concern edit UVs and not the "shadow" mesh displayed when texture painting. This will be address in a future commit. We now cache the uv mesh in the mesh batch cache and only reupload data on changes. Update could be more granular (and a bit faster) but it's not our main concern ATM. This should fix problem caused by the IMM api used to draw large meshes. This makes performance skyrocket compared to previous implementation. There is still a big CPU bottleneck when not in sync selection mode but it is not related to the drawing function directly.