Add FOM on the vm_id that executes the job

[linsword13]

This is occasionally useful as an inexact way to locate the VM that runs rank 0.

Sample output:

 modifier::GcpMetadata::machine-type = h3-standard-88
    modifier::GcpMetadata::image = projects/schedmd-slurm-public/global/images/slurm-gcp-6-6-hpc-rocky-linux-8-1721332881
    modifier::GcpMetadata::ghostname = caeslurmv6-h3nodeset-0.c.hpc-workload-performance.internal
    modifier::GcpMetadata::main-gid = 6390746155122030581
    modifier::GcpMetadata::gids = 4685835775755810805, 6390746155122030581
    modifier::GcpMetadata::project-id = 767663353010
    modifier::GcpMetadata::Level 0 Groups (cluster) = 1
    modifier::GcpMetadata::Level 1 Groups (rack) = 1
    modifier::GcpMetadata::Level 2 Groups (host) = 2
    modifier::GcpMetadata::All Hosts = e2bf4b97dbb6b9490659f4dccf029b7d/7431cbebb4a74fea0965ac21f2c4de01/f63c0e19559b2cb3622e5a3b481d7cfc,e2bf4b97dbb6b9490659f4dccf029b7d/7431cbebb4a74fea0965ac21f2c4de01/2e9aa20cd62c8f42860812d9e4e6002c