Add full screen loader and revert required Magento_SalesRule condition

[Coosos]

Hi,

In this MR I propose to add a full screen loader to avoid clicking on place order before this request starts / ends because the cart can be closed before paymentfee finished execution.

Also, I am removing / revert "require.defined" because magento can throw an exception to the sales rules, thus causing the total information to be incorrect for the payment method.

On the other hand, what is "isLoading" for ?

[mageprince]

Hi @Coosos, thank you for your contribution. We will add this improvement in the next version of the module on Magento Marketplace.

On the other hand, what is "isLoading" for?

This is an observable variable. But recently we checked that this is not used anywhere. We will check and remove that or better if you create PR for it.