Ensure job-scheduler can be a drop-in replacement for job-scheduler working in ODFE 1.13 and ES 7.10.x for v1.0.0

[dblock]

Coming from opensearch-project/OpenSearch#671 and opensearch-project/opensearch-plugins#12.

• Renaming Rest APIs
• Renaming Settings
• Renaming Indices
  

  job-scheduler/spi/src/main/java/com/amazon/opendistroforelasticsearch/jobscheduler/spi/utils/LockService.java

  Line 70 in f2c4874

  private static final String LOCK_INDEX_NAME = ".opendistro-job-scheduler-lock";

• Renaming Namespaces (E.g. com.amazon.opendistroforelasticsearch to org.opensearch)
• Renaming Classes, Methods, Variables
• Renaming all remaining identifiers (E.g Opendistro to OpenSearch).
• 100% Backward compatibility with ES v.?
• Drop in replacement for Opendistro plugins with OpenSearch plugins

[dblock]

Settings done, #20

[tlfeng]

I will take care of this today. Guide to follow with: https://github.com/opensearch-project/opensearch-plugins/blob/main/UPGRADING.md

[tlfeng]

With above PRs merged,
Rest APIs, variables, namespaces, and remaining identifiers have been renamed.
No classes and methods to be renamed.

[dblock]

@tlfeng What's left for this issue?

[tlfeng]

Hi dB, Indices renaming and testing in the real scenario are left.

[dblock]

We've decided not to rename indices.

Integration tests need to run against rc1 artifact (coming soon). That probably requires a change in CI workflow once that's available.

[dblock]

@tlfeng are we done here? close if so

[tlfeng]

Hi dB, I think it can be closed. Although you found the 'rc1' qualifier is not declared in the CI workflow (#32), it doesn't impact the compatibility of the plugin. We can also close after that is resolved.