afdo_tools: move worktree creation to git_utils

This will be needed soon by more CLs for b/332589934.

BUG=b:332589934
TEST=repo upload

Change-Id: Id91a3604e0e547de0d348e6aa01ec168e0165c50
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5435854
Reviewed-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
Commit-Queue: George Burgess <gbiv@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
2 files changed