Rename remaining types so that all begin Payment*
Modified CurrencyAmount to PaymentCurrencyAmount and ShippingOption to PaymentShippingOption.
BUG=
618754
RelatedLink=https://github.com/w3c/browser-payment-api/commit/26b092664b26cf06293a3eab462ef8c4005c82f5
Committed:
https://crrev.com/ef35132022c6123992c4e5666213b5e481b39d33
Cr-Commit-Position: refs/heads/master@{#400475}