Ensure (via auto tests) that a combination of enabled: true and enabled: false between AbstractButton and Action work

https://codereview.qt-project.org/#/c/231577/ changed the test to imperatively assign values since the test was inadvertently relying on incorrect ordering that was fixed with bdb8cf49daf4a1c7dfb9bd9caf14e19e3aa66293. We should add another auto test to ensure that declarative bindings work when both values are set.