* allow payment methods to disable based on shipping or other factors:
- renamed 'initialized' array 'available' to match primary purpose of
`canMakePayment` api - whether payment method should be available
- trigger refresh of available payment methods when shopper chooses
different shipping method
- rename resolveCanMakePayments => refreshCanMakePayments
- tweaked some variable names and scope for clarity
- added comments to clarify things
Note this should not affect behaviour yet - no existing payment methods
use this new feature. COD payment method will need this - woocommerce/woocommerce-blocks#2831
* optimise refreshCanMakePayments:
- useShallowEqual to avoid unnecessary call when shipping methods have
not actually changed (but object value has)
* replace ("set") payment methods in store, was appending:
- payment methods may come and go depending on cart/checkout state
- the previous SET action appended provided payment methods to the
collection
- this prevents dynamic payment methods e.g. COD from being able to hide
i.e. disable
* cache test payment request to avoid unnecessary stripe API calls:
- in the canMakePayment callback there's a test payment to determine if
chrome pay/apple pay is set up and available
- canMakePayment is now called multiple times as checkout state changes
- now the results of the test payment are stored in variable, and
returned on subsequent calls
* set init flag to avoid additional attempts to init stripe API:
+ tweak naming of init flag