Reland "[waffle]Override the number of search engines using cmd"

This is a reland of commit 777f2ab1

Original change's description:
> [waffle]Override the number of search engines using cmd
>
> Override the number of search engines to display a small or large list
> using command line arguments.
>
> This will make testing the UI simpler and will deflake some tests.
>
> Screen recording: http://b/329579023#comment2
>
> Fixed: b:329579023
> Change-Id: Ife5c16b1f0327228d0eb684fc83ea977b9590648
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5383505


> Reviewed-by: Nicolas Dossou-Gbété <dgn@chromium.org>
> Auto-Submit: Jack Yammine <jyammine@google.com>
> Commit-Queue: Jack Yammine <jyammine@google.com>
> Cr-Commit-Position: refs/heads/main@{#1279055}

There was a compilation issue on CFT.

Fixed: b:329579023
Change-Id: I98081de4f37635719f04b5bb8c796cd21722a449
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5402142


Reviewed-by: Nicolas Dossou-Gbété <dgn@chromium.org>
Commit-Queue: Jack Yammine <jyammine@google.com>
Cr-Commit-Position: refs/heads/main@{#1279566}