[FEATURE] Configurable global metric dimensions

[noCharger]

As a developer, I want to enable flexibility in terms of which metric dimensions to emit to avoid making a direct code modification and deployment.

[noCharger]

Also we should avoid adding EMR specific vars when publishing metrics like these

https://github.com/opensearch-project/opensearch-spark/blob/main/flint-core/src/main/java/org/opensearch/flint/core/metrics/reporter/DimensionedCloudWatchReporter.java#L370-L372

Instead they could live in Spark Env as a configurable set.

GLOBAL_METRICS_DIMENSION: {
   SERVERLESS_EMR_JOB_ID: <SERVERLESS_EMR_JOB_ID>
   SERVERLESS_EMR_VIRTUAL_CLUSTER_ID: <SERVERLESS_EMR_VIRTUAL_CLUSTER_ID>
   FLINT_CLUSTER_NAME: <FLINT_CLUSTER_NAME>
}