This cl implements shipping address/option change events for PH. With
this change payment handlers can notify the merchant when the user
changes the selected shipping address/option, and wait for updated
details (e.g. new shipping cost, etc) from merchant.

For overall flow please check
https://chromium-review.googlesource.com/c/chromium/src/+/1779003

Bug: 984694
Change-Id: Id881ba22bf4c846a4570801bacc49e5d4e89a72b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804557
Reviewed-by: Mike West <[email protected]>
Reviewed-by: Rouslan Solomakhin <[email protected]>
Commit-Queue: Sahel Sharify <[email protected]>
Cr-Commit-Position: refs/heads/master@{#700238}