Reset PWA manifest update throttling timer on browser restart

This CL changes PWA manifest update check throttling to reset on browser
restart. This is to make it easier to diagnose any issues with PWA
updating detected on live profiles by ensuring that manifest update
checks will be performed after a browser restart.

This CL adds a DesktopPWAsLocalUpdatingThrottlePersistence flag that
can quickly revert us back to the previous behaviour should we need.

Bug: 926083
Change-Id: Id9a0f9146af710922dd11cc42c114bf6dff31a3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1999902
Reviewed-by: Giovanni Ortuño Urquidi <[email protected]>
Commit-Queue: Alan Cutter <[email protected]>
Cr-Commit-Position: refs/heads/master@{#731731}
9 files changed