cv: save Cq-Depend deps to CL.Snapshot.
cv: save Cq-Depend deps to CL.Snapshot.

Tests will be coming as part of integration test
(not yet uploaded).
R=qyearsley, yiwzhang

Bug: 1146015
Change-Id: I9910180d2e8a7b09513cbec89f6977f4d24303f4
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2555438
Reviewed-by: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go