Pass required_billing_contact_fields field in apple pay session call based on dynamic fields

[ShankarSinghC]

This change is required as part of the one click checkout where in which we expect apple pay to collect the billing details from the customer and pass it in the confirm call with the payment_data.
In order for apple pay to collect the billing details from customer we need to pass"requiredBillingContactFields": ["postalAddress"] in the /session call. Hence we need to have a validation in the backend that checks for the dynamic fields for a specific connector and pass the required_billing_contact_fields to sdk.