feat(unified): add index scoring model config (#116210)

* feat(unified): add bm25 index scoring model

We want try BM25 scoring model since they have global scoring which we can probably re-use for fan-in/fan-out logic

https://github.com/blevesearch/bleve/blob/32d98823c4b7482c62cc6c847508ed7659c23c37/docs/scoring.md#global-scoring

* fix(plugins): update plugin test data

pkg/storage/unified/search/bleve_test.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/blevesearch/bleve/v2"
+	index "github.com/blevesearch/bleve_index_api"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/stretchr/testify/assert"
@@ -50,6 +51,7 @@ func TestBleveBackend(t *testing.T) {
 	backend, err := NewBleveBackend(BleveOptions{
 		Root:          tmpdir,
 		FileThreshold: 5, // with more than 5 items we create a file on disk
+		ScoringModel:  index.BM25Scoring,
 	}, nil)
 	require.NoError(t, err)
 	t.Cleanup(backend.Stop)
@@ -773,6 +775,7 @@ func setupBleveBackend(t *testing.T, options ...setupOption) (*bleveBackend, pro
 		IndexCacheTTL: defaultIndexCacheTTL,
 		Logger:        log.NewNopLogger(),
 		BuildVersion:  buildVersion,
+		ScoringModel:  index.BM25Scoring,
 	}
 	for _, opt := range options {
 		opt(&opts)