Remove Windows SVN bootstrapping and some SVN tooling. Since
"depot_tools" is no longer sync'd to SVN, and we have been committed to
Git for years now, this is obsolete. Any transition code will never
reach SVN users, and any remaining code should not be used by Chromium
developers.

BUG=chromium:630904
TEST=unit

Change-Id: Ie984e8400a748702b125eaeed8157719ef4b88cc
Reviewed-on: https://chromium-review.googlesource.com/562748
Commit-Queue: Daniel Jacques <dnj@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>