fix: restore missing batch/jobs permissions and add PVC permissions to executor role (#553)

## Problem
Customer reported that batch changes are failing with the error:
```
running command "step.kubernetes.step.0.pre": persistentvolumeclaims is 
forbidden: User "system:serviceaccount:sourcegraph-test:sg-executor" cannot 
create resource "persistentvolumeclaims" in API group "" in the namespace 
"sourcegraph-test"
```
    
## Solution
Add missing `persistentvolumeclaims` permissions (`create`/`delete` /
`get` / `list`) that the executor needs for batch change job execution,
based on customer's working role configuration.

### Checklist

- [x] Follow the [manual testing
process](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/TEST.md)
- [ ] Update
[changelog](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/charts/sourcegraph/CHANGELOG.md)
(NOT NECESSARY)
- [ ] Update [Kubernetes update
doc](https://docs.sourcegraph.com/admin/updates/kubernetes) (NOT
NECESSARY)

### Test plan
- [x] Follow the [manual testing
process](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/TEST.md)
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---------

Co-authored-by: Alex Jean-Baptiste Jr <[email protected]>
Co-authored-by: Enrique Gonzalez <[email protected]>

Author: 3 people

charts/sourcegraph-executor/k8s/templates/executor.Role.yaml

@@ -29,7 +29,10 @@ rules:
       - ""
     resources:
       - secrets
+      - persistentvolumeclaims
     verbs:
+      - get
+      - list
       - create
       - delete
 {{- end }}