Function write_mdl_with_mdx_to_vec 

pub fn write_mdl_with_mdx_to_vec(mdl: &Mdl) -> Result<MdlWriteResult, MdlError>

Writes an MDL model and its companion MDX vertex data to byte vectors.

Unlike write_mdl_to_vec, this function computes the MDX vertex buffer layout (stride, flags, per-attribute offsets) from the mesh vertex data and writes interleaved vertex attributes into a separate MDX buffer.