[FEATURE] Update neural-search stats API spec with new stats added in 3.1

[q-andy]

Is your feature request related to a problem?

Opening this issue for neural-search owners track the new stats we're adding for 3.1.0 release. In neural search we are adding multiple new stats for 3.1 to backfill existing functionality and monitor new feature launches. Each new stat will require updating the response schema for the stats API spec added in #850.

To make sure we don't miss anything, I'll reference all the PRs in this issue to have all required changes in a single place

• Add TextChunkingProcessor stats Add TextChunkingProcessor stats neural-search#1308
• Skip inference on optimized text embedding processor add stats for text embedding processors with flags neural-search#1332
• Semantic highlighter Add stats tracking for semantic highlighting neural-search#1327
• Hybrid query: Add hybrid query and score/rank based normalization processor stats neural-search#1326 (comment)
• Fixed char length chunker: Feat: Add FixedCharLengthChunker for character length-based chunking neural-search#1342
• Semantic field/neural query: Add stats tracking for semantic field neural-search#1362
• New params: Add include_individual_nodes, include_all_nodes, include_info params to stats API neural-search#1360