[omnibox] Clean up all usage of IsNewAnswerLayoutEnabled

This CL eliminates a bunch of code that depended on feature
flag kOmniboxNewAnswerLayout which is no longer needed on
desktop, and has since been repurposed for another feature
on Android.  See crrev.com/c/1405882 for additional context.

Bug: 900255
Change-Id: Id20aaeaa648807a1e257d0d80c6e8c33646acb37
Reviewed-on: https://chromium-review.googlesource.com/c/1412993
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Orin Jaworski <orinj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623534}
7 files changed