Revert "Fix typo; Documentation; Expose layer for framebuffer attachament; Add framebuffer viewport setter; Remove framebuffer restore; Expose framebuffer push/pop stack API; Remove blend modes; Remove depth_range_set; Implement GPU_face_culling, GPU_front_facing, GPU_point_size, GPU_line_width, GPU_viewport, GPU_color_mask and GPU_depth_mask"

This reverts commit 9db3d1951d.

This was an accidental commit of the patch D8826

source/blender/gpu/GPU_framebuffer.h

@@ -209,10 +209,6 @@ void GPU_framebuffer_recursive_downsample(GPUFrameBuffer *fb,
                                           void (*callback)(void *userData, int level),
                                           void *userData);
 
-void GPU_framebuffer_push(GPUFrameBuffer *fb);
-GPUFrameBuffer *GPU_framebuffer_pop(void);
-uint GPU_framebuffer_stack_level_get(void);
-
 /* GPU OffScreen
  * - wrapper around frame-buffer and texture for simple off-screen drawing
  */