[DSG] It is not clear from UI why PVs mounted on root cannot be attached to other workbenches

Description of problem:

As result of https://issues.redhat.com/browse/RHODS-5935 PV which are mounted to root folder of a workbench cannot neither be deleted or change connected workbench (until the workbench doesn't get deleted).

However, a user may not know why certain PV cannot be fully edited or deleted. A PV mounted to root doesn't even show the connected workbench in the Edit modal:

In addition, when creating a workbench, the root PVs are not displayed among the existent PV, but may not be not clear to users why.

I think we need to change a bit the UI to show sth like:

• the connected workbench while editing the root PV and make the connected workbench immutable.
• show the delete action in the 3-dots menu but disable it or enable it but prompting a warning message saying that PV cannot be deleted 
• when creating a workbench with an Existent PV, the UI should show all the PV and disable the selection for the ones which are used as root for other workbenches

these are just example, UX team could think other solutions

Prerequisites (if any, like setup, operators/versions):

Create a DS Project

Steps to Reproduce

1. create a workbench with a new PV (e.g., pv-workbench-1)
2. go back to project details page
3. click on 3-dots menu corresponding to the selected PV
4. click Edit storage
5. check the "connected workbenches" section
6. create a new workbenche and try to attach an existent PV
7. check if the previous PV shows up

Actual results:

Users may not understand why they see different UI behavior with PVs which are mounted to root folders

Expected results:

Users may easily understand why they see different UI behavior with PVs which are mounted to root folders

Reproducibility (Always/Intermittent/Only Once):

Always

Build Details:

RHODS v1.20.0-16, v1.19.1-1

Workaround:

Additional info: