Merge #4476

4476: Make the `/facet-search` route use the `sortFacetValuesBy` setting r=irevoire a=Kerollmops

This PR fixes #4423 by ensuring that the `/facet-search` route uses the `sortFacetValuesBy` setting.

Note for the documentation team (to be moved in the tracking issue): Using the new `sortFacetValuesBy` setting can slow down the facet-search requests as Meilisearch iterates over the whole list of facet values and computes the count of documents on every entry. That is hardly or even impossible to optimize correctly.

### TODO
 - [x] Create a custom HashMap wrapper for the facet `OrderBy` settings.
         This wrapper will return the `OrderBy` setting of the facet, if not defined will use the default `*` one, and if not there either (strange) will fall back on the lexicographic one.
- [x] Create a `ValuesCollection` wrapper that implements the logic for the lexicographic and count order by.
  - [x] Use it when there is no search query.
  - [x] Use it when there is a search query with and without allowed typos.
  - [x] Do not change the original logic, only use a wrapper.
- [x] Add tests

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

milli/src/update/settings.rs

@@ -14,12 +14,13 @@ use super::IndexerConfig;
 use crate::criterion::Criterion;
 use crate::error::UserError;
 use crate::index::{DEFAULT_MIN_WORD_LEN_ONE_TYPO, DEFAULT_MIN_WORD_LEN_TWO_TYPOS};
+use crate::order_by_map::OrderByMap;
 use crate::proximity::ProximityPrecision;
 use crate::update::index_documents::IndexDocumentsMethod;
 use crate::update::{IndexDocuments, UpdateIndexingStep};
 use crate::vector::settings::{check_set, check_unset, EmbedderSource, EmbeddingSettings};
 use crate::vector::{Embedder, EmbeddingConfig, EmbeddingConfigs};
-use crate::{FieldsIdsMap, Index, OrderBy, Result};
+use crate::{FieldsIdsMap, Index, Result};
 
 #[derive(Debug, Clone, PartialEq, Eq, Copy)]
 pub enum Setting<T> {
@@ -145,7 +146,7 @@ pub struct Settings<'a, 't, 'i> {
     /// Attributes on which typo tolerance is disabled.
     exact_attributes: Setting<HashSet<String>>,
     max_values_per_facet: Setting<usize>,
-    sort_facet_values_by: Setting<HashMap<String, OrderBy>>,
+    sort_facet_values_by: Setting<OrderByMap>,
     pagination_max_total_hits: Setting<usize>,
     proximity_precision: Setting<ProximityPrecision>,
     embedder_settings: Setting<BTreeMap<String, Setting<EmbeddingSettings>>>,
@@ -340,7 +341,7 @@ impl<'a, 't, 'i> Settings<'a, 't, 'i> {
         self.max_values_per_facet = Setting::Reset;
     }
 
-    pub fn set_sort_facet_values_by(&mut self, value: HashMap<String, OrderBy>) {
+    pub fn set_sort_facet_values_by(&mut self, value: OrderByMap) {
         self.sort_facet_values_by = Setting::Set(value);
     }