Replace the pointers in the MeshEdge with indexes, removing MeshPrimitive and MeshVertex.
Code cleanup proposed by the geometry nodes to make the data structures more reusable by
other areas of Blender as well. Old implementation was to focused to the texture painting.
Initial the idea was to do the same with the data structures in UVIslands, but there some
concerns were raised that requires a different design than expected from a clean-up patch.
Concerns raised about converting UVIslands:
* Maps between UVPrimitive, UVEdge and UVVertex will be stored inside the UVIsland.
During UVIsland extraction detected islands can be merged. When they are merged all
Indexes should be updated.
* It is not possible to pre-allocate all buffers as they grow, what will lead to more re-allocations. The current
implementation uses a VectorList to ensure that re-allocations don't require the data to be
moved to the newly allocated memory. We could store some information about last used
sizes in runtime data to reduce the re-allocation overhead.
* Solution would require index based access inside a VectorList, which might increase the
complexity.
* UVIslands during 3d texturing is used as intermediate data, the final data is stored as PackedPixelRows.
We could proceed converting UVIslands as well, but that would lower the performance noticeably.
3D texturing has performance requirements, so when doing so we should make sure that
it matches that as well.
Reviewed By: HooglyBoogly
Maniphest Tasks: T101740
Differential Revision: https://developer.blender.org/D16752
b9177014b6