iOS: isApplePaySupported initial state should be null when using useApplePay hook

[matthewmorgan]

Is your feature request related to a problem? Please describe.
As a developer, I would like to lay out my UI differently if I know Apple Pay is not supported, as opposed to when I am waiting to find out.

Describe the solution you'd like
Ideally, the isApplePaySupported field would be null, and updated to false or true when support status is known. Apple's HID guidelines state that

1. you should not show the Apple Pay button if the device doesn't support the payment method
2. you should render the Apple Pay button first, before other payment methods (EG a button to use Stripe's CardField.)

If the initial state were null, it would be possible to render EG an activity indicator until the state is resolved, then rendering the Apple Pay button (or not) along with the others, instead of having the UI reflow.

Describe alternatives you've considered
Laying out space for the Apple Pay button that starts blank, and stays blank unless isApplePaySupported resolves to true? But this sort of dictates a vertically stacked array of buttons, with unused whitespace, so not awesome.

Additional context
Thanks for reading!