Initialise CopyOrMoveIOTaskPolicyImpl if DLP enabled

- Changed CopyOrMoveIOTaskPolicyImpl to be initialised if DLP files restrictions are enabled.
- Moved CopyOrMove scans unittests to a separate file, where I added tests for DLP as well, given that we have already separate implementation for Policy (CopyOrMoveIOTaskPolicyImpl).

Bug: b/279158166
Change-Id: Ia20eec80d9ba1729cc851402ed5bb85286e9367f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4614744
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Steffen Seckler <sseckler@google.com>
Auto-Submit: Aya Elsayed <ayaelattar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1159860}