*Scan: Don't retrieve pool when checking pointer

IsManagedByNormalBuckets() first checks which pool the address belongs
to. This is redundant with the scanning loop, since filtering is
performed earlier. The CL aims to speed up scanning.

In addition, since we avoid going through multiple layers of functions
(including std::make_pair, std::pair ctor, std::tie), there are fewer
instrumentation instructions emitted, which helps to avoid contention
and possible timeouts on try-bots.

Bug: 11297512
Change-Id: Ib2d54361af927b3aee3427f8c0c76f4e94ae1a4b
Cq-Do-Not-Cancel-Tryjobs: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3143991


Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#918746}