Update payment registration config to include edit components

[nerrad]

This extracts payment method registration configuration changes from #1780.

We won't want to load payment methods fully in the editor context because that will include unnecessary weight for the page when full payment functionality is not required. So payment method registration includes a configuration for edit that allows payment methods to registry components that are only loaded in the editor context.

This allows for things like:

• testing for requirements and ensuring they are setup.
• potentially embedding/modifying configuration for payment methods right in the editor context (as opposed to a separate page)
• previewing what a setup payment method looks like.

In this pull I implemented the configuration changes including updating our demos and the the checkout payment method components.

I also included updating the CheckoutContextProvider so it receives (and exposes) an isEditor prop for indicating context in which the checkout is used. This, then will allow any child component to read this value from the checkout context and use it for determining alternative behaviour. In this particular pull, this is used to choose which payment method component is loaded from registered payment method configurations.

To test

There is no new user facing functionality in this pull. It is all developer side focused. Testing simply verifies there are no errors when loading the checkout block in the frontend or the backend.

[Aljullu]

Looking good. Just one comment regarding the order of the arguments of one function that I needed to change to get it to work, but if that's addressed it should be good to go. 👍

[Aljullu]

I think the order of the arguments is not correct here. Shouldn't selectedTab be the first one?

[nerrad]

ooo good catch!