[FEATURE] Expose "iterations" as workload-params

[gashutos]

https://github.com/opensearch-project/opensearch-benchmark-workloads/blob/main/nyc_taxis/test_procedures/default.json#L59

Like mentioned above, each OSB query has hardcoded number of iterations and they are not exposed as workload-params. Can we expose it as workload-params so that outside use can have better fine graned control over high throughput tests where we can have millions of iterations.