Add support to instance selection disk config and confidential compute to Dataproc

[sravani-bobbala]

Adding support to instance selection disk config and confidential compute
This pull request adds support for configuring Disk Config under Instance selection of Flexible Vms and Confidential Compute in the Dataproc ClusterGenerator.

Description

• Disk Config: Added support for Disk Config under instance selection of instance flexibility policies for all nodes. This allows users to provide a Disk Config specific to list of machine types that Dataproc can choose from.
• Confidential Compute: Added support for enable_confidential_compute and confidential_instance_type (enum with values CONFIDENTIAL_INSTANCE_TYPE_UNSPECIFIED, SEV, SEV_SNP , TDX)
  These changes allow for more flexible and secure Dataproc cluster management directly from Airflow.
  Unit tests have been added to verify that these configurations are correctly generated.

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