[iOS] Add animation to present/dismiss Reader mode content

This CL reuses the TabsClosureAnimation to present/dismiss Reader mode.
To make it possible, a `type` property is added to TabsClosureAnimation
to allow it to reveal grid cells instead of hiding grid cells (which it
still does by default). The point at which the animation starts is also
configurable instead of always using the same constant.

Video of animation in tab grid:
https://drive.google.com/file/d/1WNiziwSRtrJCyBnxk1WQnbJqenBxuwi3/view
Video of animation in Reader mode:
https://drive.google.com/file/d/1MM_S_mIh80RrmdNmrNHpKAHSz63daI5m/view

Bug: 428905890
Change-Id: Iec15919e5ac1523088654858c670321651c7055a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6791414
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Quentin Pubert <qpubert@google.com>
Reviewed-by: Aliona Dangla <alionadangla@chromium.org>
Auto-Submit: Quentin Pubert <qpubert@google.com>
Cr-Commit-Position: refs/heads/main@{#1494772}