[FEATURE]: Joining an existing collection when ucx is already installed

[nkvuong]

Is there an existing issue for this?

• [X] I have searched the existing issues

Problem statement

I may need to join a collection, even after ucx is installed

Proposed Solution

• Separate entry point, e.g. ucx join-collection
• Specify a single workspace that is part of the collection to be joined
• Specify the workspace host.
• Retrieve config.yml from the specified workspace.
• Update the config.yml with the new workspace id
• Upload the update config.yml to all workspaces in the collection

Additional Context

No response