Dedup credentials suggestions and sort them by latest usage

[cmonfortep]

Task/Issue URL: https://app.asana.com/0/488551667048375/1209453476472067

Description

We introduce the same logic to dedup credentials and sorting for Autofill Service.
That includes updating last used timestamp when we autofill outside our app, to improve UX.

Steps to test this PR

Feature 1

• install this branch
• Select DDG as autofill provider
• Create a bunch of logins (same username and passwords) for mlb.mlb.com, securea.mlb.com and www.mlb.com
• Create another login for www.mlb.com with a different username
• Visit www.mlb.com in our browser
• You will see 2 logins suggested
• Now go to another browser and visit the same site
• Ensure you only get 2 logins, same order from the autofill provider
• Select the second one
• Now go back to our browser
• Trigger again the suggestions prompt
• Ensure the order has changed now (since you selected the second one in the previous step)

UI changes

Before	After
!(Upload before screenshot)	(Upload after screenshot)

[cmonfortep]

• Dedup credentials suggestions and sort them by latest usage #5675 👈 (View in Graphite)
• develop

This stack of pull requests is managed by Graphite. Learn more about stacking.