vrend: Implement VIRGL_CCMD_CLEAR_SURFACE
As part of Virtio GPU 3D acceleration for windows clear_render_target and clear_depth_stencil are required. And as requested there they should be implemented as new command.
To support gallium clear_render_target and clear_depth_stencil command VIRGL_CCMD_CLEAR_SURFACE, that clears specific virgl surface, is introduced. It is implemented by attaching surface to blit fbo and then using code shared with vrend_clear and glClear to clear surface.
mesa counterpart: mesa/mesa!25947 (merged)
Edited by Max R