[hue] Support dynamic adding/deleting of scenes

[andrewfg]

In #16980 we added support for Automation channels. This included the introduction of a mechanism to handle resource add and resource delete events so that the Automation channels are dynamically updated.

This Issue is to suggest extending that new resource add and resource delete event support mechanism so that the list of Scenes in a Room or Zone will be dynamically updated as Scenes are added and deleted (as well as renamed).

(Additionally this new mechanism might be applied to dynamically update the list of Effects per Light. Although Effects are seldom updated, and only when Hub firmware is updated, so less important).