Add initial NetworkAnnotationMonitor

NetworkAnnotationMonitor will be used to determine which network
annotations have incorrect policy mappings. It will report via UMA the
hash_code of any annotations that were observed when they were expected
to be disabled based on policy values. Internal doc: go/regmon-chromium

This feature is set to disabled by default based on a new feature flag.
Disabled annotations are currently hard-coded; policy checking logic to
be added later.

BUG: b:315844831
TEST: out/Default/unit_tests --gtest_filter='NetworkAnnotationMonitor*'
TEST: out/Default/services_unittests --gtest_filter='NetworkService*'
TEST: out/Default/browser_tests --gtest_filter='All/NetworkAnnotationMonitor*'
Change-Id: I7543ba2b591b4d79923dfc73dd202181b64a0ec4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5120283
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Aiden Chiavatti <chiav@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1250975}