commonize job name validation

[akagami-harsh]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Fixes #2054

Checklist:

• Docs included if any changes are user facing

[google-oss-prow]

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[kannon92]

Please add some unit tests for this function.

[tenzen-y]

/hold

[tenzen-y]

This commonize does not have value since we already use the Kube validations lib here.
My expectations are commonizing replicaSpec validations:

training-operator/pkg/webhooks/pytorch/pytorchjob_webhook.go

Lines 93 to 109 in 7c5ea70

	func validateSpec(spec trainingoperator.PyTorchJobSpec) (admission.Warnings, field.ErrorList) {
	var allErrs field.ErrorList
	var warnings admission.Warnings
	if spec.ElasticPolicy != nil && spec.ElasticPolicy.NProcPerNode != nil {
	elasticNProcPerNodePath := specPath.Child("elasticPolicy").Child("nProcPerNode")
	nprocPerNodePath := specPath.Child("nprocPerNode")
	warnings = append(warnings, fmt.Sprintf("%s is deprecated, use %s instead", elasticNProcPerNodePath.String(), nprocPerNodePath.String()))
	if spec.NprocPerNode != nil {
	allErrs = append(allErrs, field.Forbidden(elasticNProcPerNodePath, fmt.Sprintf("must not be used with %s", nprocPerNodePath)))
	}
	}
	allErrs = append(allErrs, validatePyTorchReplicaSpecs(spec.PyTorchReplicaSpecs)...)
	return warnings, allErrs
	}
	func validatePyTorchReplicaSpecs(rSpecs map[trainingoperator.ReplicaType]*trainingoperator.ReplicaSpec) field.ErrorList {