[iOS] Reorganize toolbar's folder

Now that the toolbar's files have been cleaned up after UI Refresh,
the folder can be reorganized.
The files related to the fullscreen features are moved to a separate
folder. The toolbar model delegate gets its own gn target.
The resources are unused and are removed.

Bug: 800266
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I0e7043e13c2c90c6f939af55d7e447f929667681
Reviewed-on: https://chromium-review.googlesource.com/1245798
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594311}
40 files changed