Select Columns Dialog Usability & Accessibility Needs Updating

[MRayermannMSFT]

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1. When selecting no columns the message says "should be" instead of "must be". Using must makes more sense since Ok button is disabled. #7681
   ✅ merged +1
   
2. When selecting no columns the message icon is a warning instead of error. Error makes more sense because the current state is error-like and preventing the accepting of the current state. #7682
   ✅ merged +1
   
3. Visible focus is lost after using keyboard to invoke clear all, move to top, or move to bottom #7683
   ✅ merged +1
   
4. Can't select column and use "Move *" buttons using keyboard #7671
   accessibility ✅ merged +2