Move Multi-user under Cluster section of the wizard

[tmscarla]

Description

In order to enhance PCUI user experience, we need to thin out the steps of our cluster creation wizard. Following UX design, the whole Multi-user step needs to be removed, and Multi-user section needs to be placed under Cluster step of the wizard.

This PR aims at solving the issue, by conditionally showing Multi-user properties in Cluster step through a dedicated checkbox.

Changelog entry

• Remove Multi-user wizard step and embedded it into Cluster step in a dedicated section

How Has This Been Tested?

• Unit tests
• E2E tests
• Manually navigated through the end of the wizard
  • With multi-user enabled
  • With multi-user disabled

References

• https://cloudscape.design/components/checkbox/

PR Quality Checklist

• [x] I added tests to new or existing code
• [x] I removed hardcoded strings and used our i18n solution instead (see here)
• [ ] I made sure no sensitive info gets logged at any time in the codebase (see here) (e.g. no user info or details, no stacktraces, etc.)
• [ ] I checked that infrastructure/update_infrastructure.sh runs without any error
• [x] I checked that npm run build builds without any error
• [x] I checked that clusters are listed correctly
• [x] I checked that a new cluster can be created (config is produced and dry run passes)
• [x] I checked that login and logout work as expected

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