Bare Control Planes: allow for creating control planes without a config

[darkmuggle]

Description of your changes

Allow for creating a control plane without a configuration for Cloud.

I have:

• [x] Read and followed Upbound's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] Added backport release-x.y labels to auto-backport this PR, as appropriate.

How has this code been tested

Tested locally:

minerva:~/src/up $ up ctp create -a upbound bh-horcrux --configuration-name=voldemort-prod
bh-horcrux created
minerva:~/src/up $ up ctp create -a upbound bh-darkarts
bh-darkarts created
minerva:~/src/up $ up ctp list -a upbound
NAME               ID                                     STATUS   CONFIGURATION            CONFIGURATION STATUS
bh-horcrux         7b25c5a7-ef21-41fd-972c-15e8512b3784   ready    voldemort-prod           installationQueued
bh-darkarts        fb8dc677-903b-4b17-bfc2-0bf4eb5976aa   ready    n/a                      n/a