In Snapshot Debugger mode (talking to a Firebase backend), currently breakpoint expiry is not working. There are two issues:

• The backend client implementation is expected to periodically call on_idle, which triggers the breakpoint expiration checks. However the FirebaseClient is currently not calling it
• The GetExpirationTime method in the PythonBreakpoint class is currently looking for a createTime field, however in the Firebase backend case, the field is called createTimeUnixMsec, and it has a different format.