Fix flaky MMR diversification YAML tests (elastic#143706)

The default int8_hnsw index type quantizes float32 vectors to
int8, introducing enough scoring error to non-deterministically
reorder documents with close cosine similarities. With only 4
dimensions the quantization is particularly coarse.

Use explicit hnsw index type on test dense_vector mappings to
get exact float scoring and deterministic KNN result ordering.
Update expected results to reflect exact cosine ordering.

Closes elastic#143430
Closes elastic#143609

Author: mayya-sharipova

muted-tests.yml

@@ -366,15 +366,9 @@ tests:
 - class: org.elasticsearch.xpack.esql.qa.mixed.EsqlClientYamlIT
   method: test {p0=esql/40_tsdb/TS Command grouping on text field}
   issue: https://github.com/elastic/elasticsearch/issues/142544
-- class: org.elasticsearch.multiproject.test.CoreWithMultipleProjectsClientYamlTestSuiteIT
-  method: test {yaml=search.retrievers/result-diversification/10_mmr_result_diversification_retriever/Test MMR result diversification single index float type}
-  issue: https://github.com/elastic/elasticsearch/issues/143430
 - class: org.elasticsearch.repositories.azure.AzureBlobContainerRetriesTests
   method: testWriteLargeBlob
   issue: https://github.com/elastic/elasticsearch/issues/143551
-- class: org.elasticsearch.multiproject.test.CoreWithMultipleProjectsClientYamlTestSuiteIT
-  method: test {yaml=search.retrievers/result-diversification/10_mmr_result_diversification_retriever/Test MMR result diversification multiple indexes}
-  issue: https://github.com/elastic/elasticsearch/issues/143609
 - class: org.elasticsearch.index.query.PrefixQueryBuilderTests
   method: testPrefixCircuitBreakerTripsWithLowLimit
   issue: https://github.com/elastic/elasticsearch/issues/143548

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.retrievers/result-diversification/10_mmr_result_diversification_retriever.yml

@@ -23,6 +23,8 @@ setup:
               textvector:
                 type: dense_vector
                 dims: 4
+                index_options:
+                  type: hnsw
               id:
                 type: integer
 
@@ -41,6 +43,8 @@ setup:
               textvector:
                 type: dense_vector
                 dims: 4
+                index_options:
+                  type: hnsw
               id:
                 type: integer
 
@@ -76,6 +80,8 @@ setup:
               textvector:
                 type: dense_vector
                 dims: 4
+                index_options:
+                  type: hnsw
               rankfield:
                 type: integer
               id:
@@ -215,7 +221,7 @@ teardown:
   - match: { hits.hits.6._source.textbody: "ninth text" }
   - match: { hits.hits.7._source.textbody: "seventh text" }
   - match: { hits.hits.8._source.textbody: "eighth text" }
-  - match: { hits.hits.9._source.textbody: "fourth text" }
+  - match: { hits.hits.9._source.textbody: "fifth text" }
 
   - do:
       search:
@@ -308,7 +314,7 @@ teardown:
   - match: { hits.hits.6._source.textbody: "ninth text" }
   - match: { hits.hits.7._source.textbody: "seventh text" }
   - match: { hits.hits.8._source.textbody: "eighth text" }
-  - match: { hits.hits.9._source.textbody: "fourth text" }
+  - match: { hits.hits.9._source.textbody: "fifth text" }
 
   - do:
       search:
@@ -356,7 +362,7 @@ teardown:
   - length: { hits.hits: 3 }
   - match: { hits.hits.0._source.textbody: "seventh text" }
   - match: { hits.hits.1._source.textbody: "eighth text" }
-  - match: { hits.hits.2._source.textbody: "fourth text" }
+  - match: { hits.hits.2._source.textbody: "fifth text" }
 
 ---
 "Test MMR result diversification byte vector type":
@@ -459,7 +465,7 @@ teardown:
   - match: { hits.hits.6._source.textbody: "ninth text" }
   - match: { hits.hits.7._source.textbody: "third text other" }
   - match: { hits.hits.8._source.textbody: "third text duplicate other" }
-  - match: { hits.hits.9._source.textbody: "fifth text other" }
+  - match: { hits.hits.9._source.textbody: "sixth text other" }
 
   - do:
       search:
@@ -514,7 +520,7 @@ teardown:
   - match: { hits.hits.6._source.textbody: "ninth text" }
   - match: { hits.hits.7._source.textbody: "seventh text" }
   - match: { hits.hits.8._source.textbody: "eighth text" }
-  - match: { hits.hits.9._source.textbody: "fourth text" }
+  - match: { hits.hits.9._source.textbody: "fifth text" }
 
 ---
 "Test MMR result diversification rank_window_size restricts top docs":