Add VPC Routing Profile Commands to nico-admin-cli

[chet]

Site operators need a narrow command line interface for changing a VPC's routing profile and releasing the previous VNI after the site has converged.

What This Involves

• Add a command that selects the destination routing profile and accepts an optional VNI.
• Add an explicit command that releases the inactive VNI.
• Require the existing unsafe operation confirmation for both mutations.
• Use the current VPC version to reject concurrent changes.
• Verify and display the active profile and VNI returned by Core.
• Preserve Core errors for invalid profiles, unavailable VNIs, and unsupported VPC configurations.
• Do not add transition history, CSV output, or a tenant command.

Depends on #5816.

Part of #5813.