Button loading binding does not work

[evshi]

Describe the bug
Using an expression for the button loading prop does not update properly. This is because the prop is never registered as a binding it is overwritten with local state.

To Reproduce
Steps to reproduce the behavior:

1. Create a button with a loading prop and bind to some expression
2. Trigger expression to true
3. Button loading state does not update

Expected behavior
Button loading state should update

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Write tests!!!