Menu: Can't change icons option after init

The "menus" and "role" options can't be changed after init either. "position" should be fine as that applies the next time a submenu is opened, unless the expectation would be to reposition an open submenu when the position option is updated. Is it? I'd like confirmation on that (and new tickets, if necessary) before addressing this one, since there's no _setOption in menu, yet. Would handle them all at once.

I think we need to start making explicit exceptions for certain options being able to be changed after init.

menus: I don't think we should let users change options that deal with how the widget's structure is created. This is similar to accordion's header option.

role: I know some users re-use dialogs, so I could see someone wanting to change the role on a dialog (if we ever let that be customizable so you can have an alertdialog). I'm inclined to say that we don't allow changing this, and wait for good use cases to come in (if there are any).

position: We do re-position dialogs if they're open, but I think that's a pretty different situation from an open menu or open autocomplete. I'd say that changing the position while the menu is open shouldn't do anything until the next submenu is opened.

So, unless there are objections, I'd say icons is the only option to be handled.

Menu: Allow changing icons option after creation. Fixes #8927 - Menu: Can't change icons option after init

Changeset: 2c3d311f90281e95827708e2e8d0e52832a437de