Fix websocket stream reconnection

[kschiffer]

Summary

This PR fixes the automatic reconnection of event streams after a disruption.

Changes

• Fix omitted connection success event to setup the internal state machine correctly for reconnection attempts.
• Improve the synthetic event messages to reflect the new situation for disconnects after the websocket refactor.

Testing

• Go to the Console and navigate to an application or gateway
• Observe the event stream connecting and delivering events
• Put your machine into sleep mode
• Wait a couple of seconds
• Exit sleep mode
• Observe the event stream being closed
• Observe the event stream being automatically reconnected after a couple of seconds

Notes for Reviewers

START_EVENT_STREAM_SUCCESS event and hence the connection was never set as CONNECTED but CONNECTING and consequently no reconnection attempts were made because the connection was considered to be still connecting.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• The steps/process to test this feature are clearly explained including testing for regressions.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.