SHDP-433 Upgrade to SI 4.1.0

- Our custom conversion service logic broke with
  SI 4.1.0 due to its internal changes. We originally
  had our own conversion service registered order to
  customize it. We can now rely on SI's conversion
  service and add converters using @IntegrationConverter
  if @EnableIntegration is in place in @Configuration
  which is what boot would do automatically.
- Remove our own conversion service.
- Add usage of @EnableIntegration in batch annotation
  based configurations..
- Rename refs from yarnIntegrationConversionService to
  integrationConversionService.
- Add some tests to see that batch javaconfig works.