Add a `.data<T>()` method that retrieves a mutable span. This is useful
more and more as we change to filling in vertex buffer data arrays
directly, and compared to raw pointers it's safer too because of asserts
in debug builds.
Pull Request: https://projects.blender.org/blender/blender/pulls/123338
Part of #116901.
The BMesh version of the algorithm was parallelized because BMesh has
edge to face topology lookup available.
This also allows removing `GPU_vertbuf_steal_data`, by just generating
the correct data type in the first place. Removing that should help dealing
with improvements to VBO data ownership in the future.
Now that all relevant code is C++, the indirection from the C struct
`GPUVertBuf` to the C++ `blender::gpu::VertBuf` class just adds
complexity and necessitates a wrapper API, making more cleanups like
use of RAII or other C++ types more difficult.
This commit replaces the C wrapper structs with direct use of the
vertex and index buffer base classes. In C++ we can choose which parts
of a class are private, so we don't risk exposing too many
implementation details here.
Pull Request: https://projects.blender.org/blender/blender/pulls/119825
