Introduce a configurable remote metadata client AND migrate LockService to the client

[cliu123]

Description

Currently, the Job Scheduler plugin stores job metadata in a system index on the local OpenSearch cluster. However, some deployments require more flexibility in how and where metadata is stored. There is no straightforward way to configure the plugin to store job metadata outside of the local OpenSearch cluster.
This PR does 2 things:

1. introduces a configurable client wrapper that allows to configure a remote metadata store as a replacement of local system index. The
2. migrates LockService.java from OpenSearch transport client to SdkClient. Note that the SdkClient does not support remote index or DynamoDB table creation for now, so the index creation will be skipped when remote metadata store is configured. isMultiTenancyEnabled is used as a proxy of enabling remote metadata store.

Related Issues

Resolves #828

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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[codecov]

Codecov Report

❌ Patch coverage is 62.93103% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.51%. Comparing base (fd51d8f) to head (750960a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...opensearch/jobscheduler/utils/LockServiceImpl.java	61.53%	25 Missing and 10 partials ⚠️
...rg/opensearch/jobscheduler/JobSchedulerPlugin.java	60.00%	7 Missing and 1 partial ⚠️

❌ Your project status has failed because the head coverage (70.51%) is below the target coverage (75.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #831      +/-   ##
==========================================
+ Coverage   70.49%   70.51%   +0.02%     
==========================================
  Files          42       42              
  Lines        2057     2106      +49     
  Branches      165      174       +9     
==========================================
+ Hits         1450     1485      +35     
- Misses        495      505      +10     
- Partials      112      116       +4     

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[cwperks]

@cliu123 is it possible to spin up an external service for integration test purposes to simulate the remote store? i.e. let's run the integration tests of the sample plugin with remote store enabled.

Potentially DynamoDB local? https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBLocal.html

Docker images located here: https://hub.docker.com/r/amazon/dynamodb-local