Add volumeMounts to job pods

[razvan]

Description

Fixes #342

Tested with: https://github.com/stackabletech/hdfs-topology-provider/blob/feat/job-volume-mounts/test/stack/07-spark.yaml

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [x] Changes are OpenShift compatible
- [x] CRD changes approved
- [x] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [x] Helm chart can be installed and deployed operator works
- [x] Integration tests passed (for non trivial changes)
- [x] Changes need to be "offline" compatible

# Reviewer
- [x] Code contains useful comments
- [ ] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [x] Changelog updated
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added

[razvan]

CI: https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/spark-k8s-operator-it-custom/127/

[adwk67]

ah, we probably need an update to the "CRD specification" in the docs section.

[razvan]

Need to add this option to the docs/CRD section.

Tthe crd docs are now generated automatically. That's why I added this which is copied to the CRD.

[adwk67]

I mean this, which is independent of the auto-generated docs: https://docs.stackable.tech/home/stable/spark-k8s/crd-reference