Enhancements to Workspace Creation Properties

[jenny-s51]

Motivation

Follow-up to #303.

Implementation

1. Apply Stack layout for consistent spacing for "Volumes" and "Secrets" expandable sections / description.
2. Persisting the description text when the expandable section is open - currently it gets removed with the !isVolumesExpanded flag however we want to expose it in both cases.

Originally posted by @jenny-s51 in #303 (review)