[FEATURE] fix#31575 mesh layer speed rendering improvements (LOD)
As mesh layer could have millions of triangles, rendering could be very slow, especially when all the triangles are displayed in the view whereas triangles are too small to be viewed.
For those situations QGIS has an option to simplify the mesh. Simplification leads to one or more simplified mesh that represents levels of detail (LOD). When rendering the mesh, the appropriate level of detail is chosen to have an adequate rendering depending on the view.
