fix: validate allowed frozen column & alert when invalid

[ghiscoding]

• Validate that there is at least 1, or more, column to the right of the frozen column otherwise show an error (we do this check before calling setColumns()).
• Validate that the column freeze is allowed in the browser by making sure that the frozen column is not exceeding the available and visible left canvas width.
• Show an alert when 1 of these 2 are invalid, the alert message is configurable and the default to use an alert() is also configurable