[DOCS] Update ES|QL search tutorial for 9.2 (elastic#138234)

* Update ES|QL search tutorial for 9.2

- Add FORK/FUSE hybrid search with RRF
- Add RERANK for semantic reranking
- Add COMPLETION for LLM text generation
- Add KNN/TEXT_EMBEDDING for vector search
- Reorganize steps for better logical flow (FTS → filtering → combining → AI)
- Fix QSTR, RERANK, COMPLETION syntax
- Use approach-based tabs for hybrid search (OR vs FORK/FUSE)
- Add callout annotations with numbered list explanations
- Update title to 'ES|QL for search tutorial'

* Update learn more section

* remove link

* Remove keyword multi-field from description and clarify text vs keyword usage

* wrap match operator in quotes in prose for clarity

* remove OR boost tab now that we have fork/fuse

* add explicit limits to FORKs

* add note about using same embedding model for queries and docs

* provide rrf and linear combo examples in tabs

* use rerank default and rejig section accordingly

* fix FUSE linear syntax

Author: leemthompo