feat: allow for parent chunks

[mhordynski]

Feature description

Ragbits' DocumentSearch should provide a way to store information about parent chunks.

Parent chunks is approach to chunking where you divide one bigger chunk to smaller child chunks. Based on that how many of child chunks from parent chunks were retrieved, pipeline may decide to replace child chunks with full content of parent chunk.

Proposed approach is to leverage VectorStoreEntry metadata fields to store information about parent chunk, and based on that have result postprocessor replacing child chunks with parent when all criteria matches.

Motivation

Parent chunks is method of improving retrieval performance that previously worked well in projects by deepsense.ai

Additional context

No response