up ctx: Add menu item for connecting to a control plane

[cbuto]

Description of your changes

This PR adds a menu item to the space/group/control plane views that allows users to select it which saves the context and exits, just like q/f10.

Fixes https://github.com/upbound/up/issues/502

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

screenshots:

Control plane:

Group:

Space:

[RedbackThomson]

Will follow up with fixes in the next PR