*Scan: Use reservation table instead of card table while scanning

The QuarantineCardTable has better precision (4KB for card) compared to
the ReservationOffsetTable, which has 2MB (super-page) granularity.
Moving to ReservationOffsetTable will cause more frequent hits of the
scanning slow path, but at the same time aims to improve the browser
memory footprint.

cnn:2021 shows:
PMF: -5.3% (40MB -> 38MB);
Scan time: +15% (2.23ms -> 2.56ms).

Bug: 1129751
Change-Id: I311401c8f0f52f85a1c2d403fe44816eb44abf2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3010378
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#910275}