Support Painless scripts as a processor

[dlvenable]

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

OpenSearch users are often familiar with Painless script. Also, many users are looking for generic scripting as well.

Describe the solution you'd like

Create a painless processor:

processor:
- painless:
     source |
       event['total_time'] = event['connection_time'] + event['response_time']

Describe alternatives you've considered (Optional)

This could also exist alongside an expression script using existing Data Prepper expression languages.

Additional context

N/A

[AdaptiveStep]

Cool idea. But why settle with painless. Why not just offer LUA scripting in general? Seems like an easier solution.