Blender Git Loki

Fix #32941: Sequencer Preview shows texture which is apart of the window.

Issue was caused by buffer shadows were binding buffer after offscreen buffers
was bind which lead to some unpredictable results.

Made it so ED_view3d_draw_offscreen wouldn't bind any buffers and for proper
shadows ED_view3d_draw_offscreen_init should be manually be called before
drawing to an offscreen.

This should also make open gl render with AA enabled a bit faster.

Also fixed missing sequencer cache invalidation when open gl render type is
changing.

Material and Rendered modes are still a TODO for sequencer.