Route font mesh operations through renderer GL

src/renderer_gl/opengl_capabilities.h

@@ -183,6 +183,7 @@ struct OpenGlMeshUpload {
     const void* index_data = nullptr;
     std::intptr_t index_byte_count = 0;
     bool indexed = false;
+    std::uint32_t vertex_array_count = 2;
     std::span<const OpenGlVertexAttribute> attributes;
 };