This implements streaming channels using mpsc(underlying part of SSE) and SSE for sending data to clients continiously. Currently, only NETWORK event is implemented, further events will be added after the collaboration with the GUI team.

Supported platforms: all other than WASM(Simply because we can't serve a server on browser. I have a solution idea to this, but it's too early to talk about).

Enabling Event Streaming:

1. To enable event streaming, add the event_stream_configuration property to the mm2 configuration. Use the following sample values:

{
	"gui": "core_readme",
	"netid": 7777,
	// ... other parts
	"event_stream_configuration": {
		"access_control_allow_origin": "*",
		"active_events": {
			"NETWORK": { "stream_interval_seconds": 0.5 }
		}
	}
}

2- Start mm2 and wait for the initialization log message similar to: mm2_net::network_event:54] INFO NETWORK event is activated with 0.5 seconds interval.

3- Open examples/sse/index.html in your browser; events should start appearing on the screen.

Client-Side Filtering:

By default, clients listen to all events activated on the mm2 side. If you're interested in specific events, you can filter incoming events (using the filter query string parameter) to reduce network overhead.

For instance, open examples/sse/index.html with a text editor and append ?filter=TEST,DEMO,BALANCES to the EventSource url. After that, you will no longer receive NETWORK events. (Note that currently we only stream NETWORK events on mm2 side. Filtering out the NETWORK event will result in no events being received.)

Helps to #1901