Print the connect agent version in `up version`

[jastang]

Description of your changes

Give users a bit more info when attaching a space to Upbound.

The agent version is hardcoded for now but we may support more functions like update in the future.

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

➜  darwin_arm64 ./up version
Client:
  Version:     v0.29.0-rc.0.168.gcf62706.dirty
  Go Version:  go1.22.2
  Git Commit:  cf62706
  OS/Arch:     darwin/arm64
Server:
  Crossplane Version:        v1.15.3-up.1
  Spaces Controller Version: Upbound Cloud Managed
Connect Agent:
  Connect Agent Version: 0.0.0-408.g343d295