Investigate how to speed up codespace creation

[agardnerIT]

How do we improve the startup time / experience of the codespace?

• Where is the time spent?
• What can move to the image (and be prebuilt?)
• What can be optimised?

[agardnerIT]

Why are we building the container from a Dockerfile every time?

• Can we prebuild this?

Why are we restarting argocd & waiting for argocd to restart?

Why are we restarting backstage & waiting for backstage to restart?

Can some of the downloads (like gh CLI and argocd) be moved to the Dockerfile?