[iOS][ReminderNotifications] Set page title for reminder notifications

This change updates the ReminderNotificationClient to attempt to set the
page title on scheduled reminder notifications based on the active
WebState. If the title cannot be determined or the conditions are not
met, the notification will fall back to displaying the page URL.

Change-Id: I85aaa3c09be1272f33f200ca1f48d1adb951984d
Bug: 392921766
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6628855
Reviewed-by: Scott Yoder <scottyoder@google.com>
Commit-Queue: Benjamin Williams <bwwilliams@google.com>
Cr-Commit-Position: refs/heads/main@{#1472380}