Set Zero Buffer as the default buffer for OpenSearch API source

[MohammedAghil]

Is your feature request related to a problem? Please describe.
At present, OpenSearch API source uses the Blocking Buffer as the default buffer. But for OpenSearch API source, the default buffer should allow a synchronized way to pass the data prepper events from source to sink.

Describe the solution you'd like
Set the default buffer for OpenSearch API source to ZeroBuffer

Additional context

• Open Search API source

[dlvenable]

@MohammedAghil , Within Data Prepper we allow configuring the buffer using the YAML. We should keep the default behavior as it is.