mcp: support sse (#243621)

* mcp: support sse

Didn't seem like Claude Desktop configs have SSE support yet, but I did
the obvious of having an object with a `url`. I also added a `type`
(optional for stdio) so we can better disambiguate types of configs.

Example .vscode/mcp.json:

```
{
  "servers": {
    "everything": {
      "type": "sse",
      "url": "http://localhost:3001/sse"
    }
	}
}
```

Closes #243242

* update layer check