GCP Batch: Support passing standard machine types to the Google backend

[javiergaitan]

Description

Currently, and as described in #7535, only general-purpose machine types are supported in Google Backend, which prevents running wdl workflows on many machine types available on GCP, including those provisioned with modern GPUs.

I believe the simplest and most general solution would be to pass the machine type directly from the wdl configuration to the Google Batch API. The idea is that this approach would be more resilient to machine types being added or deprecated on GCP, as users would only need to update their wdl workflows in such cases. An alternative approach of mapping machine specs (e.g.: cpu platform and gpu requirements) to standard machine types would potentially introduce an additional layer of maintenance with little benefit.

This PR adds support for a new standardMachineType key in the runtime section, which is only parsed for the Google backend.

Testing

I deployed this internally and verified I can successfully run the following wdl workflow:

version 1.0

task nvidia_smi {
    input {
        String docker_version
    }

    command <<<
        nvidia-smi

        touch .done
        echo "Finished at $(date)"
    >>>

    runtime {
        docker: <internal image>
        disks: "local-disk 50 SSD"
        memory: "32G"
        preemptible: 0
        gpuCount: 1
        gpuType: "nvidia-tesla-a100"
        standardMachineType: "a2-highgpu-1g"
    }

    output {
        File done = ".done"
    }
}

workflow nvidia_smi_wf {
    input {
        String docker_version
    }
    
    call nvidia_smi  as nvidia_smi_call {
        input:
            docker_version = docker_version
    }

    output {
        File done = ".done"
    }
}

Next steps

• Confirm this approach is in the right direction with the cromwell team.
• Work on proper unit tests and get this PR ready to be merged.

Release Notes Confirmation

CHANGELOG.md

• I updated CHANGELOG.md in this PR
• I assert that this change shouldn't be included in CHANGELOG.md because it doesn't impact community users

Terra Release Notes

• I added a suggested release notes entry in this Jira ticket
• I assert that this change doesn't need Jira release notes because it doesn't impact Terra users

[javiergaitan]

@aednichols @mcovarr : Please let us know if you have any feedback on this PR. I would like to confirm this is in the right direction before working on tests and getting this ready for merging. Alternatively, please let me know if I should reach out to someone else for review.

[jgainerdewar]

Thanks for taking the time to submit this! Unfortunately the maintaining team doesn't have much bandwidth to collaborate on community contributions right now, but we'll keep it in mind for the future.