fix: Support custom error format for Route53 ChangeResourceRecordSets operation

[epau]

This PR adds support for a custom error format that is sometimes returned by the ChangeResourceRecordSets operation in the Route53 service.

The custom error looks something like the following:

<?xml version="1.0" encoding="UTF-8"?>
<InvalidChangeBatch xmlns="https://route53.amazonaws.com/doc/2013-04-01/">
  <Messages>
    <Message>Tried to create resource record set duplicate.example.com. type A, but it already exists</Message>
  </Messages>
  <RequestId>b25f48e8-84fd-11e6-80d9-574e0c4664cb</RequestId>
</InvalidChangeBatch>

Issue #

#214

New/existing dependencies impact assessment, if applicable

Conventional Commits

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[epau]

This PR is targeting the epau/feat/support-crt-0.5.0 branch since it depends on changes made there. The target branch will be updated to main once epau/feat/support-crt-0.5.0 merges.

[epau]

It would be awesome to have a way to just write this in swift, since it isn't dependent on the smithy model.
I filed this issue to investigate some mechanism that would allow us to write service specific swift code. I imagine the solution here will be related (if not the same) as solving the service specific integration test problem.

[ganeshnj]

public APIs/structs must have docs.

[epau]

This isn't public. This is just internal as it's just used for decoding and then it's transformed into a InvalidChangeBatch instance.

[ganeshnj]

LGTM, just small comment on docs.