feat: Combine regexes targeting same fields

[Darkheir]

Description

Combine regexes targeting same field and let the regex creation fail if the limit is reached.

How was this PR tested?

Describe how you tested this PR.

[Copilot]

Pull request overview

This PR optimizes search warmup for regex-based queries by coalescing multiple regex patterns that target the same (field, json path) into a single multi-pattern automaton, reducing redundant term-dictionary traversals and making combined-regex construction a strict failure point when limits are hit.

Changes:

• Coalesce regex automatons per field+path into a single Automaton::Regex(..., Vec<String>) and deduplicate/sort patterns before warmup.
• Update warmup logic to build a combined regex automaton via tantivy_fst::Regex::from_patterns(...) and fail warmup if the combined regex cannot be built.
• Add tests covering regex coalescing behavior and warmup failure on unbuildable combined regex; bump patched tantivy-fst revision.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
quickwit/quickwit-search/src/leaf.rs	Build a combined regex automaton from multiple patterns during warmup and add a regression test for failure behavior.
quickwit/quickwit-doc-mapper/src/query_builder.rs	Coalesce regex automatons by (field, path) and add tests for field-limit behavior and coalescing semantics.
quickwit/quickwit-doc-mapper/src/doc_mapper/mod.rs	Update Automaton::Regex to hold multiple patterns (Vec<String>) and adjust tests accordingly.
quickwit/Cargo.toml	Update the patched tantivy-fst git revision.
quickwit/Cargo.lock	Lockfile update corresponding to the patched tantivy-fst revision bump.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.