Support load imagery by id instead of only URL

[wille]

The remote control imagery command requires the URL param to work. It would be good if we could use also the id of the imagery layer, instead of only the URL. Example: /imagery?id=Maxar-Premium

iD already supports it with the background URL param, that way JOSM could have the same behaviour.

The reason: It's common that projects on Tasking Manager need to be mapped with one of the global imagery like Bing, Mapbox, ESRI and Maxar. We would like to make it easier to project managers to choose which imagery the project should use and also avoid publishing the tokens on the web. That way we could load the task to the mappers/validators with the correct imagery in a straightforward way.

[simon04]

In 17655/josm:

fix #20660 - Remote control /imagery: add imagery by id

[simon04]

Documentation: Help/RemoteControlCommands?action=diff&version=24

[simon04]

In 17724/josm:

fix #20730, see #20660 - Remote control /imagery: add imagery by id (also all layers)