Add support for network tags in Google Batch executor

[ejseqera]

New feature

Add support for network tags when running Nextflow pipelines on Google Batch. This would allow users to specify network tags in their Nextflow configuration that will be applied to the Google Batch job's allocation policy.

Use case

Network tags are used in GCP to apply firewall rules and manage network access for compute instances. When running Nextflow pipelines on Google Batch, users might:

• Apply specific firewall rules to their compute instances
• Control ingress/egress traffic based on tags
• Manage network security at scale across multiple pipeline executions
• Ensure compliance with organizational network security policies

Suggested implementation

The implementation would involve:

1. Add networkTags property to the BatchConfig class to store the configuration
2. Update GoogleBatchTaskHandler to add the tags to the AllocationPolicy when creating Google Batch jobs
3. Add appropriate warning(s) when tags are specified with instance templates for example

Example config:

google {
    project = 'tower-cloud-testing'
    location = 'europe-north1'
    batch.spot = true
    batch.networkTags = ['nextflow-test']
}