[iOS] Change uses of BVC tab creation methods to use TabModel.

This CL removes the remaining public and private BVC tab creation methods, and instead factors callers to directly call into the tab model.

Bug: 90338
Change-Id: I44231cf05816130875dd17f5892f43a7389ed402
Reviewed-on: https://chromium-review.googlesource.com/c/1329742
Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614675}
3 files changed