Fix: OpenGL based point cloud is empty if depth mapping texture is not provided

[vahapt]

See: https://github.com/IntelRealSense/realsense-ros/issues/3206 When called through realsense-ros package, depth mapping texture is not provided, thus point cloud is not generated. A new shader is generated to handle the case.

[sysrsbuild]

Can one of the admins verify this patch?

[Nir-Az]

@vahapt thanks for your contribution. It might take some time but we will review this PR.

[Nir-Az]

@ashrafk93 any new inputs here?

[ashrafk93]

@ashrafk93 any new inputs here?

Hi, still no. I saw some drops on pointcloud generated frames with D455. Need to dig deeper