Support the bindings to be more integrable with a system's coherent memory management.
Pleaes note that thorvg now only allow the desinated memory allocators here:
malloc -> tvg::malloc
calloc -> tvg::calloc
realloc -> tvg::realloc
free -> tvg::free
issue: https://github.com/thorvg/thorvg/issues/2652
ThorVG pImpl idiom caused internal data to be scattered
across hierarchical classes. This refactoring consolidates
the data by inheriting pImpl internally, reducing memory
allocation counts and eliminating unnecessary strategy methods.
Implement some advance blending equation in GLEngine by using two
RenderPass.
* The first pass render the content into an off-screen framebuffer, also
blit the screen content to an off-screen Texture.
* The second pass renders the final blended color to the screen.
Also use a stencil test to prevent non-drawn areas from participating in the color blending calculation.
issue: https://github.com/thorvg/thorvg/issues/2435
