[Feat]: Ability to remove nodes from "All nodes" room settings about netdata-cloud

[ralphm]

Alternative suggestion: show a grayed out version of the remove-from-room button with a tooltip that suggests removal from the space settings.

Reasoning:

• This makes the UI consistent between rooms without overloading the All Nodes room with more space-level functions.
• The All Nodes room is really a type of room with dynamic membership. Once we get to have [https://github.com//issues/918], All Nodes will be just an instance of this.
• The space settings allow for quickly removing more than one node.

Note

The All Nodes room is a special case because we needed a place to put nodes that weren't explicitly assigned to another room. It is currently also the place where you get to see audit type events. For large numbers of nodes, the metrics tab will eventually hit some limits, technically, in terms of usefulness, as well as cognitive utility. There is some consensus on the concept of an All Nodes room not being ideal, but we haven't come up with a decent alternative yet.