Reland "[iOS][PageInfo] Add field trial config"

This is a reland of commit 045ea056

Original change's description:
> [iOS][PageInfo] Add field trial config
>
> Bug: 1512580
> Change-Id: I8a7e8ac4a2a63a2ca40091b7418cb9e968dc7129
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5392565


> Commit-Queue: Filipa Senra <fsenra@google.com>
> Reviewed-by: Christian Dullweber <dullweber@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1278875}

Bug: 1512580
Change-Id: I67a1bbfee16eb73f9eb36cfaaecfec9d6a62d0ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5401703


Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Christian Dullweber <dullweber@chromium.org>
Auto-Submit: Filipa Senra <fsenra@google.com>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283105}