Add search parameters argument to Vamana batch iterator construction

The code issue referenced below is leaded by Vamana batch iterator limitations where search parameters always pulled from the parent index:

In the filtered-search path, this temporarily mutates the underlying index’s search parameters (`set_search_parameters`) inside a `const` method. This is not thread-safe if the same index instance is searched concurrently (different calls can race and restore the wrong parameters). Prefer an API that passes search parameters directly to the iterator/search, or protect the mutation with synchronization (or clearly document that concurrent searches are unsupported when using filters/params).

_Originally posted by @Copilot in https://github.com/intel/ScalableVectorSearch/pull/297#discussion_r2988693394_