forms: Revisit several small issues for "info" field

  * Use the title of "Information" with internal tag of "info"
  * Add "Visibility" column to UI and retire "Required" and "Internal"
    columns
  * Add visibility selection to new fields and show visibility to the user
    information fields when displayed on the ticket details form
  * Make the visibility settings translatable
  * Use constants internally for visibility configuration detection
  * Use a larger input when managing the information HTML content
  * Fix validation errors for new fields
    * Enforce new field name uniqueness
    * Enforce new field name character validation