Rename podSpec to podTemplate and podDistruptionBudget to podDistruptionBudgetTemplate

[kvaps]

As part of #109

• move podSpec.extraArgs to options
• remove podSpec.extraEnvs, podSpec.resources, podSpec.image, podSpec.imagePullPolicy as they will be available to override in spec.podTemplate.spec.containers["etcd"] (see Add the ability to specify volumes and containers #113)
• rename podSpec to podTemplate
• rename podDistruptionBudget to podDistruptionBudgetTemplate
• move all the parameters from podSpec.metadata to podTemplate.metadata
• move all the parameters from podSpec to podTemplate.spec

---
apiVersion: etcd.aenix.io/v1alpha1
kind: EtcdCluster
metadata:
  name: test
  namespace: default
spec:
   replicas: 3
+  options: # map[string]string
+    arg1: "value1"
+    arg2: "value2"
-  podSpec:
-    image: "quay.io/coreos/etcd:v3.5.12"
-    imagePullPolicy: Always
-    extraArgs: # map[string]string
-      arg1: "value1"
-      arg2: "value2"
-    extraEnvs: # []core.v1.EnvVar Ready k8s type
-      - name: MY_ENV
-        value: "my-value"
+  podTemplate:
    metadata:
      labels:
        env: prod
      annotations:
        example.com/annotation: "true"
+    spec:
      imagePullSecrets:  # core.v1.LocalObjectReference Ready k8s type
      - name: myregistrykey
      serviceAccountName: default
-  podDistruptionBudget: {}
+  podDistruptionBudgetTemplate: {}