[CI] Add dCache compatibility with CTA Helm charts

Description

This MR:

• Adds support for deploying dCache in such a way that it can communicate with CTA
  • In doing so, ensure that the structure of deploying the disk buffer is consistent between EOS and dCache
• Adds a simple archival test for dCache
• Removes various eos-specific configurations from the CTA charts
• Removes various redundant mounts in the grpc statefulset
• Makes the different users specified in the client pod more configurable

Checklist

• Documentation reflects the changes made.
• Merge Request title is clear, concise, and suitable as a changelog entry. See this link

References

Closes #304 (closed)