helm chart - add support for emptyDir storage type

[tomeresk]

What problem are we solving?

Currently, the supported storage types are either persistent, or hostPath, so for ephemeral storage generally hostPath is used (e.g. logs storage).
hostPath mounts a directory from the host node's filesystem and can pose a security risk on shared/multi-tenant k8s clusters, so its usage is often restricted.
Adding support for emptyDir storage gives another option for ephemeral storage, which does not pose a security risk on shared/multi-tenant K8s cluster, so is generally allowed

How are we solving the problem?

Adding support for the emptyDir storage type in all places that allow defining a storage type.
This PR introduces emptyDir as a new option, and if it's not explicitly used in the values.yaml file, it has no effect on existing users.

How is the PR tested?

Tested a deployment on a local K8s cluster, verifying that volumes were created as emptyDir when configured for it, uploading and downloading files

Checks

• I have added unit tests if possible.
• I will add related wiki document changes and link to this PR after merging.