[ios] Fix ContextMenuTestCase on iOS 26 device

This CL fixes the failures in ContextMenuTestCase on iOS 26 device by
- extending the long press duration from 1 second to 2 seconds
- updating the page title for iOS 26 and above in the share action
- use `waitForUIElementToAppearWithMatcher` instead of asserting an
  element to make sure that the element is visible

Fixed: 437302773, 437305940, 437293861, 437292479
Change-Id: I6045295ec2ce6fde23469e3f47426e4b38308b94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6846220
Commit-Queue: Asami Doi <asamidoi@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1502617}