[FEATURE] Softer validation of corpora workload parameters for vectorsearch benchmark

[finnroblin]

Is your feature request related to a problem? Please describe

Currently each workload corpus requires a target index parameter when there are multiple indices. However, the vector search bulk ingest workload operation (bulk-vector-data-set) does not use this target index when ingesting data. Instead, users specify the target index as a parameter in the custom-bulk ingest operation in their test procedure.

I'm opening this issue because the target-index parameter is required at workload validation time despite it being unnecessary for vector search workloads. As a result the VS workload.json must contain unused parameters.

Describe the solution you'd like

One solution is to make the target-index corpora parameter optional at validation time. Perhaps it's also possible to enforce that either the parameter is specified in the corpora in workloads.json or that bulk-vector-data-set is used in a test procedure.

Describe alternatives you've considered

I don't have all the context for why there are two ways of specifying the target index for ingesting data but I believe it's due to vector datasets being in hdf5 format and the normal bulk operation requiring json documents.

Additional context

There is another issue stemming from VS ingestion being different than normal ingestion — Issue 317 in the workloads repo requests a VS feature that's available in non-VS workloads. I think the lack of feature parity is due to the vector-bulk operation being different from the normal bulk operation.