Let merchants customize the Card Element logo display

vmarchuk → made their first commit to this issue’s fork.

I've reviewed this and think it needs a little work.

Ultimately, I think we should not keep the "Enable credit card icons" field on the form. It's confusing to have to check that checkbox in order to activate showing payment method logos, even though "No" is an option in the select list. In other words, when the form is rendered and there is a value for the old setting, it should be used to set the values of the new settings in an equivalent fashion ... but we shouldn't be trying to preserve and interpret the checkbox after this update.

@rszrama

Ultimately, I think we should not keep the "Enable credit card icons" field on the form. It's confusing to have to check that checkbox in order to activate showing payment method logos, even though "No" is an option in the select list. In other words, when the form is rendered and there is a value for the old setting, it should be used to set the values of the new settings in an equivalent fashion ... but we shouldn't be trying to preserve and interpret the checkbox after this update.

It's done. I also updated the settings to set the default credit cards for backwards compatibility. This means that if someone after updating the module opens the payment gateway settings form and then just clicks "Save", we will keep the existing behavior but with the new settings.