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Before this CL, autofill payment apps are always ranked below other
types of payment apps, including just-in-time installable (but not yet
installed) service-worker based pyament handler.

This CL introduces a new payment app ranking order behind a feature flag
such ranks payment apps first by types:
1. Installed 3rd-party payment handlers
2. Complete autofill instruments
3. Just-in-time installable 3rd-party payment handlers
4. Incomplete autofill instruments

Within each group, payment apps are sorted by frecency as before.

Bug: 1046875
Change-Id: I34ed0fec1f7b6fc4fbf8c6984d0893c3fad73443
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2028740
Commit-Queue: Danyao Wang <danyao@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737048}