[PROPOSAL] Relocate Job Scheduler into core as a native plugin

Based on this discussion, Job Scheduler will be relocated to core as a native plugin.

Draft PR to relocate Job Scheduler to native plugins : https://github.com/opensearch-project/OpenSearch/pull/5453

As this change is currently slated for the 2.5.0 release, work has begun to prepare for and facilitate this relocation. This issue shall be used to track the associated work items and discuss any questions / concerns.

Build and Assemble Workflow Modifications Since Job Scheduler acts as a dependency for other plugins (AD, IM, Reporting), relocating this project within core as a native plugin will necessitate changes to the yml schema of the input manifest used to assemble the full distribution of OpenSearch.

Discussions for the input manifest changes has been started here .

Dependent Plugin Modifications Though moving Job Scheduler to native plugins is not necessarily a breaking change, the path to Job Scheduler snapshots will be affected. Plugins that have Job Scheduler as a dependency will require modifications to their respective build.gradles [1]. These modifications will be handled by the OpenSearch core Extensibility team (will handle the code changes and testing) and we shall tag the respective plugin owners to review our changes. Additionally, we would like some input on the right naming convention for Job Scheduler [2].

• [1] Job Scheduler artifacts are currently uploaded to and consumed from https://aws.oss.sonatype.org/content/repositories/snapshots/org/opensearch/opensearch-job-scheduler/, upon relocation, these artifacts will now be uploaded to https://aws.oss.sonatype.org/content/repositories/snapshots/org/opensearch/plugin/opensearch-job-scheduler/
• [2] Dependent plugins reference opensearch-job-scheduler as part of their extendedPlugins within their build.gradle, (here is Anomaly Detection’s reference for example). Upon relocation, in order to maintain native plugin naming conventions, it is our intention to rename this project as job-scheduler, which would require dependent plugins to also modify their extendedPlugins reference. However, if there are any objections to this change, please discuss this below.

Plans to support previous versions of Job Scheduler In order to support security patches to previous versions of Job Scheduler, upon relocation, the original Job Scheduler repository will not be archived.

[praveensameneni]

LGTM

[joshpalis]

@prudhvigodithi @nknize @dblock @vibrantvarun @praveensameneni @sean-zheng-amazon @anirudha @bbarani @gaiksaya @peterzhuamazon

For the dependent plugin owners, please let us know if you have any questions / concerns regarding items [1] and [2]. We shall move forward with raising these PRs starting December 5th.