Fixed OS select dropdown + switched to FormField for consistency with the rest of wizard

[BarcoMasile]

Description

This PR fixes a bug with the OS select dropdown which showed the dropdown option label and value as a concatenated string. It also switches to a formfield wrapping the select for consistency with the rest of the wizard, also fixing a layout issue where the select would adapt to the width of the current selection, forcingly wrapping other option strings when the dropdown was open.

Changes

• improved and typed itemToOption funcion + added test for it
• switched to FormField wrapping a Select for OS, Vpc and Region selection in second step of the wizard

How Has This Been Tested?

• unit tests
• e2e tests
• manual testing

PR Quality Checklist

• [x] I added tests to new or existing code
• [] I removed hardcoded strings and used our i18n solution instead (see here)
• [x] 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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