[0.5-nexus] Fix ci for scheduler on nexus branch

[seankao-az]

Description

Test related to external scheduler in this branch were failing for:

2024-10-30T19:12:11.4327415Z 24/10/30 19:12:11 ERROR OpenSearchAsyncQueryScheduler: Error creating index : .async-query-scheduler
2024-10-30T19:12:11.4329032Z java.lang.NoSuchFieldError: USE_FAST_DOUBLE_PARSER
2024-10-30T19:12:11.4330525Z 	at com.fasterxml.jackson.dataformat.yaml.YAMLParser._parseNumericValue(YAMLParser.java:1055)
2024-10-30T19:12:11.4332267Z 	at com.fasterxml.jackson.core.base.ParserBase.getNumberType(ParserBase.java:660)
2024-10-30T19:12:11.4333764Z 	at com.fasterxml.jackson.core.JsonGenerator._copyCurrentContents(JsonGenerator.java:2616)
2024-10-30T19:12:11.4335439Z 	at com.fasterxml.jackson.core.JsonGenerator.copyCurrentStructure(JsonGenerator.java:2547)
2024-10-30T19:12:11.4337495Z 	at org.opensearch.common.xcontent.json.JsonXContentGenerator.copyCurrentStructure(JsonXContentGenerator.java:418)
2024-10-30T19:12:11.4339633Z 	at org.opensearch.common.xcontent.json.JsonXContentGenerator.writeRawField(JsonXContentGenerator.java:361)
2024-10-30T19:12:11.4341505Z 	at org.opensearch.common.xcontent.XContentBuilder.rawField(XContentBuilder.java:1000)
2024-10-30T19:12:11.4343400Z 	at org.opensearch.client.indices.CreateIndexRequest.innerToXContent(CreateIndexRequest.java:368)
2024-10-30T19:12:11.4347630Z 	at org.opensearch.client.indices.CreateIndexRequest.toXContent(CreateIndexRequest.java:356)
2024-10-30T19:12:11.4349317Z 	at org.opensearch.common.xcontent.XContentHelper.toXContent(XContentHelper.java:476)
2024-10-30T19:12:11.4351154Z 	at org.opensearch.client.RequestConverters.createEntity(RequestConverters.java:819)
2024-10-30T19:12:11.4352673Z 	at org.opensearch.client.RequestConverters.createEntity(RequestConverters.java:814)
2024-10-30T19:12:11.4354283Z 	at org.opensearch.client.IndicesRequestConverters.createIndex(IndicesRequestConverters.java:162)
2024-10-30T19:12:11.4356349Z 	at org.opensearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1907)
2024-10-30T19:12:11.4358282Z 	at org.opensearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1894)
2024-10-30T19:12:11.4360038Z 	at org.opensearch.client.RestHighLevelClient.performRequestAndParseEntity(RestHighLevelClient.java:1858)
2024-10-30T19:12:11.4361613Z 	at org.opensearch.client.IndicesClient.create(IndicesClient.java:159)

which is compatibility issue between the Jackson YAML parser and the version of Jackson core libraries being used in this branch.

This PR convert the configuration files to JSON. JSON is natively supported and doesn't require additional parsers.
Having green CI would help with more confidence in backporting PRs.

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[noCharger]

let's ensure CI pass