* restructure event-emit directory and convert emitters to promises
- also add emitEventWithAbort function
* implement event emitters as promises
* clean up logic
- return from for loop
- define response as const on each iteration.
- return true if loop completes successfully.
* rename event_emit folder to event-emit
- restructures `@woocommerce/base-context` imports so it pulls from `index.js` in the `base/context` folder. That way tree-shaking will be used if possible. This also helps with organizing the folder structure a bit better for the new contexts.
- Fixes all the various imports through the code due to the above change.
- Adds `CheckoutContextProvider`, `useCheckoutContext` and related files.
- Adds `PaymentMethodDataProvider`, `usePaymentMethodDataContext` and related files.
- Adds `ShippingMethodDataProvider`, `useShippingMethodDataContext` and related files.
- Adds typedefs used for the various context interfaces.
Darren Ethier