Do not call schedule render every invalidate, only on setting properties and children

[agubler]

Type: bug

The following has been addressed in the PR:

• There is a related issue
• All code matches the style guide
• Unit or Functional tests are included in the PR

Description:

Calling scheduleRender every time invalidate is called is problematic in certain scenarios when a widget is wrapped by the ProjectorMixin.

1. When the widget has a property registered with a custom diff that always returns changed as true i.e. diffProperty('my-prop', always)
2. Uses the new @alwaysRender decorator (such as the Container HOC).

Currently this causes projector instances to continuously schedule a render, as this.invalidate() will be called for all __setProperties__ calls.

Overriding invalidate in this way should not be needed, as a listener that calls scheduleRender is attached to projector instances' invalidated event.

Instead this invalidated event can be explicitly emitted at the end of setProperties and setChildren, the public API for projector instances.

Other mechanisms such as injectors of external state that need to schedule a render, also emit an invalidated event and therefore will be sure scheduleRender is fired.