feat(machines): Add 'Register as DPU' to Add Machine form MAASENG-3948

[ndv99]

Blocked by #5566, which will need to be merged first.

Done

• Added "Register as DPU" as an option to the "Add machine" form
• (drive-by) Removed row/col elements on Add machine form, as they haven't been needed since we transitioned to using side panels.

QA steps

• Add VITE_APP_DPU_PROVISIONING = true to your .env.local
• Go to the machine list and click "Add machine"
• Ensure a checkbox labelled "Register as DPU" is displayed at the bottom of the form.

Fixes

Resolves MAASENG-3948

Screenshots

Notes

Happy to change the position and text of the checkbox as needed.

[webteam-app]

Demo

Jenkins

demos.haus

[tmerten]

QA: Works
Code: 👍