Fix some IWYU issues around absl APIs

These files were relying on internal absl includes to pull in
absl::make_unique and absl::WrapUnique. The former can just be
std::make_unique which requires no extra includes. The latter has a base
version, so let's just use that until/unless we ever decide to align on
the absl one.

Bug: 1373619
Change-Id: I157104a415ae71bd268556b7bf601d46661d85e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4858866
Reviewed-by: Ben Kelly <wanderview@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Sébastien Lalancette <seblalancette@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1196004}