Add option to set search quality during insertion

Search quality during insertion is not currently configurable. Based on the dataset, the required search quality for insertion can vary and it should be configurable.

No file, test, or entry point is named. Start by tracing the C++ insertion path and how search quality is currently selected, then determine the option's intended scope from surrounding APIs and tests; done means callers can configure insertion search quality and existing behavior remains covered.

Written by the indexing model from the issue text.