Refactor and Remove package level variables

[renuka-fernando]

Purpose

• Fix https://github.com/wso2/k8s-api-operator/issues/461
• Ignore adding certs with same alias
• Ignore adding kaniko job volumes with same name
• Remove package level vars,
  • kaniko volumes, docker file properties, HPA configs
• Introduce the following structs.
  • kaniko.JobProperties

    type JobProperties struct {
      DockerFileProps *DockerFileProperties
      certAliases     map[string]struct{}
      Volumes         []corev1.Volume
      VolumeMounts    []corev1.VolumeMount
    }

  • mgw.HpaProps

    type HpaProps struct {
      MetricsHpaV2beta1 []v2beta1.MetricSpec
      MetricsHpaV2beta2 []v2beta2.MetricSpec
      HpaMaxReplicas    int32
    }