Improve how the space data is updated in the Camera screen

[jbphet]

Currently, the space data in the camera screen is updated using a method called _pollSpaceUrl. There are a few problems with the way this works, and I think I just ran into one of them. The problems are:

• If a request for the space data takes a long time, it is possible for a second one to be initiated. If the user happens to switch spaces while in this window, it can cause a cycle of requests for two different spaces.
• The way the polling currently works, it continues even when the screen isn't showing, which wastes processor power and probably initiates a lot of unnecessary requests to the database.
• Since the current method always sets a timer to poll for the next update, there is no clear separation between the update code and the polling code, and it would be easier to maintain and reuse if there were.

[jbphet]

I've implemented this. So far, I like it a lot. I'm not longer able to create situations with competing and out-of-sync requests for space updates, and the polling stops when the tab is not visible.

Assigning to @BLFiedler and @jessegreenberg to review the concept and the code changes. We should also decide if the same thing should be done for the Editor page.

[jessegreenberg]

Nice, that looks great! Its been working well for some time now. Even though you can't change spaces on the Editor page, the second two benefits in https://github.com/phetsims/paper-land/issues/78#issue-1673911043 make me think its worth it to o the same change for the Editor page.

[brettfiedler]

We've deemphasized Editor in favor of Creator, but should anyone use Paper Playground and want more functionality from the Editor, they might consider implementing this. Leaving as a wishlist.