Include version in GetPipeline response

[mpwoz]

Is your feature request related to a problem? Please describe.
GetPipeline doesn't include pipeline version

Describe the solution you'd like
The ES ingest/get_pipeline API includes a version field in the response: https://www.elastic.co/guide/en/elasticsearch/reference/current/get-pipeline-api.html
This is needed for making concurrency-safe updates to an existing pipeline (e.g. adding a processor)

The Nest client does not include this field in the response. https://github.com/elastic/elasticsearch-net/blob/master/src/Nest/Ingest/GetPipeline/GetPipelineResponse.cs

Describe alternatives you've considered
Right now, I'm considering falling back to the low-level REST Api, but would prefer to use the high level nest API as it already includes everything I need (except version) https://github.com/elastic/elasticsearch-net#falling-back-to-elasticsearchnet

Additional context

[stevejgordon]

Thanks for catching and raising this @mpwoz. I've fixed this in #6085 which will go out in the next release.