[Enhancement] Use index mapping json file

[ylwu-amzn]

Use java code to construct index mapping is error-prone. Let's create index mapping json file like AD https://github.com/opensearch-project/anomaly-detection/tree/main/src/main/resources/mappings

[pyek-bot]

Can you assign this to me please?

[dhrubo-os]

@pyek-bot assigned to you.