the socket events: "rgb", "depth" and "objects" aren't being emitted anywhere

## Type of Issue
The socket event handlers introduced [here](https://github.com/facebookresearch/droidlet/blob/main/dldashboard/web/src/StateManager.js#L126), [here](https://github.com/facebookresearch/droidlet/blob/main/dldashboard/web/src/StateManager.js#L127) and [here](https://github.com/facebookresearch/droidlet/blob/main/dldashboard/web/src/StateManager.js#L128) aren't being emitted anywhere in the backend and we are still emitting the [previous_event](https://github.com/facebookresearch/droidlet/blob/4f1485a47a0893a438ab5b7fe4bc552bc1d8e40b/locobot/agent/perception/perception.py#L243) and these components are being set by that.

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- [x] Refactor request
- [ ] Documentation Ask