Add rescore_vector parameter option to quantized vector index types

[benwtrent]

Description

While we have added rescore_vector available at query time, it would be useful for it to simply have default behavior that is configurable at the index level.

Consequently for the dense_vector index type, we should add a new parameter to the quantized index types that allow rescore_vector to be directly configured.

In addition to this, we need the ability to "disable" rescore_vector via some value. I would expect this to be oversample: 0. This would mean don't rescore, either in the configuration or at query time.

If the user provides a rescore_vector parameter at query time, what ever the default in the index, the query time parameter is used.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[benwtrent]

PR: #124581 addresses this.

Related issues:

• Default bbq vector indices to oversample #125158
• Add ability to bypass default vector oversampling and rescoring #125157