* [#1111] Use consistent return types for available_monitors()
Always use `impl Iterator<Item = MonitorHandle>` instead of
`AvailableMonitorsIter`. Fix an example that used the Debug
implementation of `AvailableMonitorsIter`.
* [#1111] Update changelog
* [#1111] Remove AvailableMonitorsIter type completely
* [#1111] Remove doc references to AvailableMonitorsIter