[UPMLocalUsers] Track which read/write requests were issued for the

purpose of settings migration

Not every failed attempt to read/write password settings is part of the
settings migration, so it's tracked if the read/write operations were
started as part of migration or not.

This CL pipes the information about read/write requests being part of
the settings migration. The follow-up uses the information in the
settings service.

Bug: b/331171867
Change-Id: I7fb2c179eb80e33c23bb2ebf9b80a67aad123d2d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5397679


Commit-Queue: Ivana Žužić <izuzic@google.com>
Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282536}