Add the ability to hide the stable/unstable checkbox

[zepumph]

From https://github.com/phetsims/special-ops/issues/189, we need to be able to hide this checkbox. While I could create an entire wrapper over in https://github.com/phetsims/special-ops/issues/189 just to toggle a visibleProperty, I think it is much easier and more maintainable to create a query parameter to achieve the same thing.

Matching priority of the parent issue.

[zepumph]

@jbphet would you please review this change. What do you think?

[jbphet]

@zepumph - I've added a comment to the spot where the checkbox is optionally added, other than that the change looks fine.

One question: Do we know whether this is something that we need to support long term? I'm wondering if we could set up a calendar reminder and delete this in six months or so. I know it's not a lot of code, but it's nice to remove customizations when they're no longer needed just to keep the code clean.

[zepumph]

That's a really good thought and idea. I know we have hacked a bunch in the past in balancing-act, arithmetic, and others. There seems to be no easy way to revert that or to know when this isn't needed anymore. I feel the same way about our custom wrappers like phet-io-wrapper-hookes-law. Marking for phet-io meeting.

[samreid]

This relates to the more general issue https://github.com/phetsims/phet-io/issues/1756. If the research scientist could have used studio, he could have made that customization from studio. We decided to leave the query parameter until we have a replacement plan. On hold for now.