Reset wizard state when a different region is selected

[mendaomn]

Description

This PR sparks from issues related to the fact that the selected KeyPair does not get cleared correctly when a new region is selected.

In order to fix this, and many other issues, the wizard state is re-initialized when a new region is selected.

Changes

• re-initialize wizard state when a new region is selected
• move keypair selection from the Cluster section to the HeadNode section

How Has This Been Tested?

• manually:
  • dry-run with a specific key-pair selected (passes)
  • go back and change region
  • leave key-pair as is (None, in this case)
  • dry-run passes again

PR Quality Checklist

• I added tests to new or existing code
• I removed hardcoded strings and used react-i18next library (useTranslation hook and/or Trans component), see an example 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
• I checked that npm run build builds without any error
• I checked that clusters are listed correctly
• I checked that a new cluster can be created (config is produced and dry run passes)
• I checked that login and logout work as expected

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