Set default GIT_DEPTH to 1 in Duo Workflow jobs definition

What does this MR do and why?

Set GIT_DEPTH=1 to all Duo Workflow jobs by default and allow users to override defaults when starting a workflow.

This is desired when cloning a large project like gitlab-org/gitlab, where this step only is taking too long during Duo Code Review workflow jobs.

References

Related to #572184 (closed)

Related to #573987 (closed)

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