Provide "copilot mcp" subcommand for mcp setup

### Describe the feature or problem you'd like to solve

Use `copilot mcp` to list/add/edit/delete MCP settings

### Proposed solution

In Codex CLI, Claude Code, and Gemini CLI, there is a `mcp` subcommand to list, add, edit, or delete MCP settings. This feature greatly enhances developer experience. Hopefully, the Copilot CLI will include this functionality as well.

### Example prompts or workflows

```
codex mcp add myDocServer --env API_KEY=abcdef123 -- npx -y @upstash/context7-mcp
```

### Additional context

_No response_