views/pods: use wildcard for all option in pod variable

`pod` variable could contain thousands of options in some environments.
Selecting `all` options would mean dashboard will include all of them into the PromQL
query and potentially cause issues on processing.
Switching to wildcard `.*` instead will prevent sending huge queries to database and dashboard
will continue to work for any environment.

See #129

dashboards/k8s-views-pods.json

@@ -2600,6 +2600,7 @@
         "useTags": false
       },
       {
+        "allValue": ".*",
         "current": {
           "selected": false,
           "text": "",