Automate creation of GDK version bump MR

Context

This is part of Implement auto deployments for the Container Re... (&7998 - closed) but with a lower priority since the GDK is not central to the auto-deployment plan

Problem

While GDK is an internal tool and not a deployment priority there is still the need to manually update the GDK to use the newly pushed CNG image

"${registry_image:-registry.gitlab.com/gitlab-org/build/cng/gitlab-container-registry:vX.Y.Z-gitlab}"

Solution

Create a new CI job to programmatically create version bump MR in https://gitlab.com/gitlab-org/gitlab-development-kit.