[lldb][mcp] Get the running MCP server connection information (#162752)
Currently AFAICT we don't have a way to get the MCP server socket after
it started. So this change introduces a new `protocol-server` subcommand
that allows us to query the location of a running server:
```
(lldb) protocol-server start MCP listen://localhost:0
MCP server started with connection listeners: connection://[::1]:36051, connection://[127.0.0.1]:36051
(lldb) protocol-server get MCP
MCP server connection listeners: connection://[::1]:36051, connection://[127.0.0.1]:36051
(lldb) protocol-server stop MCP
(lldb) protocol-server get MCP
error: MCP server is not running
```