Changes to add Shielded VMs support in google_dataproc_workflow_templ…

[modular-magician]

• Updated DCL version to 1.19.0 to include the shielded vms option in google_dataproc_workflow_template .
• Added Shielded VMs option in google_dataproc_workflow_template::gce_cluster_config and this would also address : Add support for shielded instance configuration in google_dataproc_workflow_template #10565

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Release Note Template for Downstream PRs (will be copied)

dataproc: added option `shielded_instance_config` to resource `google_dataproc_workflow_template`.

Derived from GoogleCloudPlatform/magic-modules#6481

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