Implement Search() in Infinity in GO (#13645)

### What problem does this PR solve?

Implement Search() in Infinity in GO.

The function can handle the following request. 
"search '曹操' on datasets 'infinity'" 
"search '常胜将军' on datasets 'infinity'"
"search '卓越儒雅' on datasets 'infinity'"
"search '辅佐刘禅北伐中原' on datasets 'infinity'"

The output is exactly the same as  request to python Search()

### Type of change

- [ ] New Feature (non-breaking change which adds functionality)

internal/engine/types/types.go

@@ -43,6 +43,10 @@ type SearchRequest struct {
 	SimilarityThreshold    float64 // Minimum similarity score (default: 0.1)
 	VectorSimilarityWeight float64 // Weight for vector vs keyword (default: 0.3)
 
+	// Sorting and ranking
+	OrderBy     string             // Order by field (e.g., "field1 desc, field2 asc")
+	RankFeature map[string]float64 // Rank features for learning to rank
+
 	// Engine-specific options (optional, for advanced use)
 	Options map[string]interface{}
 }