Move the logic for automatically reconnecting to the WebSocket after an
unexpected disconnection from the `Socket` WebSocket wrapper class to
the `StreamerService` service. The Socket class is now responsible only
for notifying the caller of unexpected disconnections.

Letting StreamerService handle reconnection ensures that a fresh
WebSocket URL, with a current access token, is used on each attempt. The
previous approach would re-use the same URL on each attempt. This could
lead to an obsolete access token being used, with the result that the
WebSocket connection degraded to an unauthenticated one and not all
expected updates were received.

As part of this change, the logic for calculating the retry delay has been
simplified and no longer uses the `retry` package, hopefully making the
behavior easier to understand.