[iOS] BWG Overflow Menu entrypoint start the BWG Flow

Prior to that CL, the Ask BWG entrypoint opened the Action Menu. Now,
Ask BWG entrypoint starts the BWG Flow.

Bug: 419065994
Change-Id: If5c797ddb726bc2d3bc0e7072cd1481eab48c40a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6641912
Reviewed-by: Joemer Ramos <joemerramos@google.com>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Prasanaa Vingadassamy <prasanaa@google.com>
Cr-Commit-Position: refs/heads/main@{#1474843}