Clean up the heartbeat Jetbrains's plugin

[akosyakov]

It should use the supervisor info endpoint instead of env vars to get information about workspace.

[loujaybee]

@akosyakov Since we've got it tracked in the GA epic, let's drop from Groundwork for now, and we can move in when we finish private + open beta 🙏

[corneliusludmann]

If for some reason we were able to fetch the status but for a moment aren't able, we will send a heartbeat(wasClosed=true) reducing the timeout to a few minutes.

For that reason I would argue it would be better to handle the exception in the HeartbeatService, retrying and being careful about setting the this.status only after successful execution.

#6551 (comment)