Reland "[iOS] EG Test for FRE Segmented Default Browser Promo"

This is a reland of commit 52688a75aba5c4aad69f331db1e1704c3c4dd5ed. Tests were failing on checks for iPad tailored strings in default browser promos, which are dependent on a feature that is disabled by default. Fixed by enabling feature for iPad tailored strings in default browser promos for this test.

Original change's description:
> [iOS] EG Test for FRE Segmented Default Browser Promo
>
> This change adds an automated UI test for personalized messaging in
> the First Run Default Browser promo.
>
> Fixed: 356878058
> Change-Id: I937b763d541c1a19ad4b46be3266b2ba8ef4a1b9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5782088
> Reviewed-by: Hira Mahmood <hiramahmood@google.com>
> Commit-Queue: Eric Ekey <ericekey@google.com>
> Reviewed-by: Benjamin Williams <bwwilliams@google.com>
> Reviewed-by: Rohit Rao <rohitrao@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1341939}

Fixed: 360376318
Change-Id: I98eb13b790df0e2b7e25958b3814841dfa2438e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5793636
Reviewed-by: Benjamin Williams <bwwilliams@google.com>
Reviewed-by: Hira Mahmood <hiramahmood@google.com>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Eric Ekey <ericekey@google.com>
Cr-Commit-Position: refs/heads/main@{#1343726}