refactor(connector): airwallex convert init payment to preprocessing (#4842)
Files to modify:


**enums.rs**
  Add:
    - function: pub::is_pre_processing_required_before_authorize

**airwallex.rs**
  Remove:
    - function: private::execute_pretasks
  Add:
    - impl: impl api::PaymentsPreProcessing for Airwallex

**transformers.rs**
  Modify existing code

**payments.rs**
  Modify existing code

**flows.rs**
  Modify existing code

**authorize_flow.rs**
  Modify existing code