Update package naming to be org.opensearch.dataprepper from com.amazon.dataprepper

[laneholloway]

Is your feature request related to a problem? Please describe.
The project is in the opensearch project and the naming should likewise be adjusted.

Describe the solution you'd like
com.amazon will be replaced with org.opensearch in all files

[dblock]

You might find https://github.com/opensearch-project/opensearch-plugins/blob/main/UPGRADING.md#opensearch-plugins useful in case there's more than just namespace renaming.