Lazy scorers (#2726)

* Refactoring of the score tweaker into `SortKeyComputer`s to unlock two features.

- Allow lazy evaluation of score. As soon as we identified that a doc won't
reach the topK threshold, we can stop the evaluation.
- Allow for a different segment level score, segment level score and their conversion.

This PR breaks public API, but fixing code is straightforward.

* Bumping tantivy version

---------

Co-authored-by: Paul Masurel <paul.masurel@datadoghq.com>

examples/snippet.rs

@@ -50,7 +50,7 @@ fn main() -> tantivy::Result<()> {
     let query_parser = QueryParser::for_index(&index, vec![title, body]);
     let query = query_parser.parse_query("sycamore spring")?;
 
-    let top_docs = searcher.search(&query, &TopDocs::with_limit(10))?;
+    let top_docs = searcher.search(&query, &TopDocs::with_limit(10).order_by_score())?;
 
     let snippet_generator = SnippetGenerator::create(&searcher, &*query, body)?;