[reader mode] Create the ReaderModeBottomSheet and show it

* Plumb through the dependencies to create the bottom sheet in the
  toolbar controller.
* Create the bottom sheet on-demand, and show if conditions allow.
* Destroy the bottom sheet along with the toolbar controller.

Bug: 431036903
Change-Id: I178fc1c259186832ff9910c94ac06c8e0bbcbc33
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6757632
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Brandon Wylie <wylieb@google.com>
Cr-Commit-Position: refs/heads/main@{#1487881}