Redesign UI for the creation of the persistent storage

• It should explain what is the persistent storage. Currently it does so pretty poorly but people kind of get it…

During the user testing of Additional Software beta:

• P3 didn’t think that connecting to the Wi-Fi could be automated, even after creating a persistent volume.
• P5 thought that someone who would find the USB stick could know which additional software was configured.

Related issues

• Related to #15109
• Related to #10048
• Related to #14544
• Related to #5881 (closed)

Original created by @sajolida on 15572 (Redmine)