Migrated Auth Reversal Integration Test to xt

In xt/author/auth-reversal.t
  Refactored to perform tests on all 4 card types

In xt/author/auth-reversal-reject.t
  Now performs tests for use cases:
    Reverse an Authorization with a Bad Request ID
    Reverse an already reversed Authorization
    Reverse an already captured Authorization
    Reverse a declined Authorization