Refactor InvoiceModule to rely on external PaymentModule

[gabrielstoica]

Breaking changes

• InvoiceModule has been refactored to PaymentModule and some of its methods (related to the ERC-721 compliance) have been removed; Also, Invoice struct has been renamed to `PaymentRequest, method names were updated to createRequest, payRequest, cancelRequest, withdrawRequestStream;
• There's a new approach on how we're retrieving the status of a request, by relying on a dynamic method called statusOf. This method relies on two new booleans added to the PaymentRequest struct, wasCanceled and wasAccepted. Depending on the payment method, either stream or transfer, it first checks the status of the stream on the Sablier protocol to see if the payment amount was fully streamed or not.
• A part of the InvoiceModule has been refactored as a periphery contract, called InvoiceCollection. This contract allows an EOA/multisig to mint ERC-721 tokens for any off-chain invoice, based on the payment recipient, invoice metadata URI and payment request ID;

[V1d0r]

Aligns with the latest flow!
With the PaymentRequest and InvoiceCollection structure we will need to rely on the external worker to generate the invoices based on the events.