project: Add missing imports

Some imports were missed when moving manifestProject to project.py

Bug: https://bugs.chromium.org/p/gerrit/issues/detail?id=15861
Change-Id: Id8fffeaa3f88f344a13b5ab44e5403c7edd98f31
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/335554


Tested-by: LaMont Jones <lamontjones@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Raman Tenneti <rtenneti@google.com>