feat(query-builder): Add easy multi-select while holding ctrl/cmd

[malwilley]

This adds the "Hold Ctrl/⌘ to select multiple" text and behavior that was in the Figma designs. You could already click the checkbox for this behavior, this makes it possible to do with the keyboard now as well.

https://github.com/user-attachments/assets/22fce3ec-089e-45a2-b040-1781f9867839