Enable NoCookieChangeNotificationOnLoad by default

This enables the feature that prevents CookieMonster from sending a
CookieChangeDispatcher notification when storing cookies loaded from the
persistent store. All other cookie changes still produce a change
notification as usual.

The base::Feature is retained to allow for emergency disabling in case
of breakage. It will be cleaned up in a subsequent CL once this change
has landed and we're confident that it doesn't break anything.

Bug: 1169280
Change-Id: Iacc589f7469cffe647cd40d31a1c3025e2fcbcf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2824192
Auto-Submit: Lily Chen <chlily@chromium.org>
Commit-Queue: Maksim Orlovich <morlovich@chromium.org>
Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#872411}