OpenSearch source with alternative sort/search_after #6332

Is your feature request related to a problem? Please describe.

The opensearch source performs search queries against the OpenSearch cluster/domain/collection to find data. To paginate, it also uses the sort and search_after query parameters.

The sort and search_after only use a combination of _score and _id. This works well for many pipeline authors as this behavior does not presume any specific field. However, some pipeline authors may want to query using @timestamp or perhaps another field they have.

Describe the solution you'd like

I'd like a configuration to configure the sort and search_after values. There should be only one option since these should be in sync. Additionally, we should be able to control ascending or descending.

source:
  opensearch:
    search_options:
      sort: 
        - name: @timestamp
           order: descending
        - name: _id
           order: ascending

Describe alternatives you've considered (Optional)

Some alternative syntax options:

Compact, but also not a pattern found in Data Prepper:

source:
  opensearch:
    search_options:
      sort: 
        - @timestamp: descending
        - _id: ascending

Split sort and order.

source:
  opensearch:
    search_options:
      sort: 
        - @timestamp
        - _id
      order:
        @timestamp: descending
        #_id: ascending  # Not required since it is the default

Additional context

N/A