Merge #5288

5288: Improve AI logging r=dureuill a=Kerollmops

This PR fixes #5285 and brings the changes from #5233 to simplify debugging indexation and search performance issues related to AI. The following texts can be found in the logs to debug and understand performance issues:

 - `embed_one: search` represents the time we spent waiting for the embedding generation, i.e., OpenAI, local HuggingFace, Ollama.
 - `filtered_universe: search::universe` the time spent filtering the documents.
 - ~`next_bucket: search::vector_sort` is the time spent finding the nearest neighbors (ANNs) in the vector store (arroy), locally~ was being triggered too many times.
 - `indexing::vectors` is the time arroy spends indexing the new vectors for a batch.
 - `documents::extract vectors` and `documents::merge vectors` to see the time spent generating and writing the embeddings.

Co-authored-by: Kerollmops <clement@meilisearch.com>

crates/milli/src/vector/mod.rs

@@ -611,6 +611,7 @@ impl Embedder {
         }
     }
 
+    #[tracing::instrument(level = "debug", skip_all, target = "search")]
     pub fn embed_one(
         &self,
         text: String,