Display total amount setting

Overview

This PR adds functionality by creating a 'Display Total Amount' setting that allows the user to choose if they want that field hidden or not.

Before

Radiobuttons hides the 'Total Amount' field by default, without the option of users choosing to show/hide the field.

After

Now, users will be able to select 'Yes' or 'No' for whether or not the total amount is displayed.

Considerations

• This setting is created with a default of 'No', so as not to break existing users' experience. Instead it is something that they can opt in to displaying.
• The condition that currently hides the total amount field is maintained, this setting is an additional check for hiding the field.
• Since Pricesetvisibility also hides the Total Amount field, I've created a PR that does the same thing as this one on that extension. However, this new setting on Radiobuttons overrides the same setting on Pricesetvisibility if both extensions are enabled.
  • As such, does it makes sense to have the same functionality in two different extensions, or should determining whether the 'Total Amount' field is displayed be handled by only one of the two?