Centralize UI event loop for Aspire CLI

The `PublishCommandBase` currently implements an event-loop to process RPC messages from the AppHost to the CLI when processing steps/tasks emitted by the AppHost. We need a similar event-loop to process RPC messages from the AppHost that support the prompting functionality. For prompting, we need to expand this behavior to commands that are not `publish`/`deploy`. We should consider centralizing the event loop that manages request/response-based patterns from the AppHost so that all CLI commands can hook into it.