Rename "base/macros.h" => "base/ignore_result.h"

This file only contains ignore_result() and is no longer a collection of
macros.

This change fixes a couple of missing IWYU removals as well.

Bug: 1010217
No-Try: true
Change-Id: Iaad1aaa48343e86b0429898bd55e4f0c56222852
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3279210
Commit-Queue: Peter Boström <pbos@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Owners-Override: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#941411}
NOKEYCHECK=True
GitOrigin-RevId: 2e6be1400ab678f21d871d0d3a1199912967324f
1 file changed