Remove support for deprecated Prepper plugins

[sbayer55]

Is your feature request related to a problem? Please describe.
Remove ambiguity in pipeline configuration YAML files and Plugins by supporting a single name for Processors/Preppers.

Describe the solution you'd like
Remove support for the the Prepper plugin type and remove support for the prepper name within the pipeline configuration YAML.

Describe alternatives you've considered (Optional)
n/a

Additional context
This change will be dependent on all DataPrepper provided plugins migrating to the new Processor plugin type.

Tasks

• Remove Prepper plugin support in code (PR Remove deprecated prepper plugin type #1707)
• Update usage of prepper: to processor: in OpenSearch Documentation website (PR: Rename prepper to processor in pipeline configuration sample for Data Prepper  documentation-website#1056)

[dlvenable]

We currently support either of the following configurations:

prepper:
  - copy_value:
  - delete_value

processor:
  - copy_value:
  - delete_value

After this change we will only support processor.

[dlvenable]

We should also search the code base for any samples, tests, or documentation that is still using the deprecated preppers:. These should all be changed to use processor: instead.

[cmanning09]

@dlvenable is PrepperState a part of the Prepper deprecation? I am concerned we may have missed providing a migration path.

[dlvenable]

We should remove this as well. Ideally, we would have added a deprecation path here. But, I believe it only affects plugin authors, not end user. So I think we should go ahead and rename it.

[oeyh]

@cmanning09 @dlvenable Thanks for looking into it!

PrepperState is implemented by MapDbPrepperState, so I assume this should be renamed to MapDbProcessorState as well? I will add those changes to the open PR #1707.

There will still be plugins, classes, and variables still with "prepper" in their names (mostly in data-prepper-plugins, e.g., ServiceMapStatefulPrepper, GrokPrepper). For those, I will open an issue in case we want to do a thorough cleanup in the future.

[dlvenable]

I think we can rename those as part of 2.0. They names visible to pipeline authors do not have prepper in them, so we are just renaming class names.