[iOS][WhatsNew] Added new features and assets for M125 What's New

This CL adds the following features to What's New:
PWMWidget, PinnedTabs and InactiveTabs.

Auto-generated via What's New script

Change-Id: Ifec07e240433b48d92fb61bce6ca1aef500e8563
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5420030


Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Auto-Submit: Nicolas MacBeth <nicolasmacbeth@google.com>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Reviewed-by: Robbie Gibson <rkgibson@google.com>
Reviewed-by: Cheick Cisse <cheickcisse@google.com>
Cr-Commit-Position: refs/heads/main@{#1283126}