Follow up the initial conversion of `StreamerService` from a function to
a class but converting instance fields from local variables in the
constructor to properties and methods from closures to object methods.

In the process some unused public APIs were removed:

 - Remove the public `reconnect` method

 - Remove the public `configMessages` field

 - Rename the internal `_connect` helper to `_reconnect` and make it
   always close the existing connection if open