Use a single instance of OopsDialog

[pixelzoom]

Related to https://github.com/phetsims/equality-explorer/issues/192 and #195 ...

OopsDialog is currently instantiated from a couple of places in the sim: EqualityExplorerSceneNode and SeparateTermsDragListener. The latter is problematic, because SeparateTermsDragListener is itself dynamic, so I can't use a PhetioCapsule there.

Since OopsDialog is modal, I think a better approach would be to eagerly create a single (global) instance of OopsDialog, use it wherever an OopsDialog is needed, and set it's StringProperty to display the desired message.

[pixelzoom]

Since OopsDialog is modal, I think a better approach would be to eagerly create a single (global) instance of OopsDialog, use it wherever an OopsDialog is needed, and set it's StringProperty to display the desired message.

That is unfortunately not possible. Attempting to instantiate a Dialog as a static global results in a failure of this assertion in Dialog.ts:

      sim: getGlobal( 'phet.joist.sim' ),
...
    assert && assert( options.sim, 'sim must be provided, as Dialog needs a Sim instance' );

So in the above commit, I'm using one static instance of OopsDialog per screen for the "numer too big" message. I still need to address the OopsDialog in SeparateTermsDragListener.

[pixelzoom]

Done.

We now have 3 static instances of OopsDialog, under equalityExplorer.global.view.dialogs. EqualityExplorerSceneNode is responsible for creating those instances at startup. There are no PhetioCapsules involved.

I've also added documentation about how to test these dialogs, see EqualityExplorerSceneNode.ts.

Closing.