msi: Upgrade to Wix Toolset 6.x

[slide]

Updates the MSI build to use Wix Toolset 6.x, which includes support for Arm64 MSIs and various improvements. This involves restructuring the project files, adding new custom actions, and updating the build scripts accordingly.

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[slide]

Need to make sure this is biuldable on the release infra.

[timja]

merge conflict

[timja]

Need to make sure this is biuldable on the release infra.

This would make jenkins-infra/release#212 (comment) fixable.

This really needs resolving: #235