Add validator for Terraform version and SlurmGCP6

[mr0re1]

$ make && ./ghpc create tst.yaml -w
**************** building ghpc ************************
validator "test_tf_version_for_slurm" failed:
Error: Using a newer version of Terraform can lead to controller replacement on reconfigure for Slurm GCP v6

Please be advised of this known issue: https://github.com/GoogleCloudPlatform/hpc-toolkit/issues/2774
Until resolved it is advised to use Terraform 1.4.0 with Slurm deployments.

To silence this warning, add flag: --skip-validators=test_tf_version_for_slurm

One or more blueprint validators has failed. See messages above for suggested
actions. General troubleshooting guidance and instructions for configuring
validators are shown below.

- https://goo.gle/hpc-toolkit-troubleshooting
- https://goo.gle/hpc-toolkit-validation

Validators can be silenced or treated as warnings or errors:

- https://goo.gle/hpc-toolkit-validation-levels

validation failed due to the issues listed above
$ make && ./ghpc create tst.yaml -w --skip-validators=test_tf_version_for_slurm
**************** building ghpc ************************
Creating deployment folder "orlovtst" ...
To deploy your infrastructure please run:

./ghpc deploy orlovtst ...