dig some values in case the values are not set

General MR

Summary

We needed a few more digs to handle optional values in Thanos

This pulls in the changes from this MR which had been reverted and adds a few more digs to allow install without passing in test-values.yaml : !4957 (merged)

TEST RESULTS:

Without passing in test-values.yaml

$ kubectl get pod -n thanos -L app,version
NAME                                     READY   STATUS    RESTARTS   AGE   APP      VERSION
thanos-query-677fbdff8c-b99tz            2/2     Running   0          73s   thanos   v0.36.1
thanos-query-frontend-544495d8b6-6f5dq   2/2     Running   0          73s   thanos   v0.36.1

With test-values.yaml passed in

$ kubectl get pod -n thanos -L app,version
NAME                                     READY   STATUS    RESTARTS   AGE     APP      VERSION
thanos-compactor-6cc65c5656-8rmlp        2/2     Running   0          66s     thanos   v0.36.1
thanos-minio-pool-0-0                    3/3     Running   0          55s     minio    
thanos-query-6666545dd9-8g55s            2/2     Running   0          66s     thanos   v0.36.1
thanos-query-frontend-544495d8b6-6f5dq   2/2     Running   0          7m13s   thanos   v0.36.1
thanos-storegateway-0                    2/2     Running   0          66s     thanos   v0.36.1

Upgrade Notices

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