[FilesBulkPinning] Tag HTTP requests with throttle ID from DriveFS

Since M115 DriveFS is moving to the new Chrome networking stack. This
means we can tag the individual HTTP requests such that we can throttle
the individual requests if required.

Bug: b:267707630
Change-Id: Idd4eb5fb41ec6b37947a7c4192659bf3ccb7c9e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4561106


Auto-Submit: Ben Reich <benreich@chromium.org>
Reviewed-by: François Degros <fdegros@chromium.org>
Commit-Queue: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1149444}