refactor: use the built-in max/min to simplify the code (#17059)

### Summary

In Go 1.21, the standard library includes built-in
[max/min](https://pkg.go.dev/builtin@go1.21.0#max) function, which can
greatly simplify the code.

Signed-off-by: futurehua <futurehua@outlook.com>

internal/engine/elasticsearch/chunk.go

@@ -959,10 +959,7 @@ func (e *elasticsearchEngine) Search(ctx context.Context, req *types.SearchReque
 		return nil, fmt.Errorf("index names cannot be empty")
 	}
 
-	offset := req.Offset
-	if offset < 0 {
-		offset = 0
-	}
+	offset := max(req.Offset, 0)
 	limit := req.Limit
 	if limit <= 0 {
 		limit = 30
@@ -1353,10 +1350,7 @@ func searchAfterPaginate(
 	// Skip phase: walk past `offset` hits without retaining them.
 	remainingSkip := offset
 	for remainingSkip > 0 {
-		batch := remainingSkip
-		if batch > common.SearchAfterBatchSize {
-			batch = common.SearchAfterBatchSize
-		}
+		batch := min(remainingSkip, common.SearchAfterBatchSize)
 
 		resp, err := fetch(ctx, baseQuery, batch, cursor, firstCall)
 		firstCall = false
@@ -1390,10 +1384,7 @@ func searchAfterPaginate(
 	// target) regardless of how many we asked for in this iteration.
 	for collectedTake < limit {
 		want := limit - collectedTake
-		batch := want
-		if batch > common.SearchAfterBatchSize {
-			batch = common.SearchAfterBatchSize
-		}
+		batch := min(want, common.SearchAfterBatchSize)
 
 		resp, err := fetch(ctx, baseQuery, batch, cursor, firstCall)
 		firstCall = false
@@ -2857,10 +2848,7 @@ func calculatePagination(page, size, topK int) (int, int) {
 
 	window := rerankWindow(size, topK)
 
-	offset := (page - 1) * window
-	if offset < 0 {
-		offset = 0
-	}
+	offset := max((page-1)*window, 0)
 
 	return offset, window
 }

internal/engine/elasticsearch/chunk_test.go

@@ -459,10 +459,7 @@ func paginate(total, size, topK int) (window, capN int, surfaced []int) {
 			block = append(block, i)
 		}
 		begin := globalOffset % window
-		end := begin + size
-		if end > len(block) {
-			end = len(block)
-		}
+		end := min(begin+size, len(block))
 		surfaced = append(surfaced, block[begin:end]...)
 	}
 	return window, capN, surfaced

internal/engine/elasticsearch/metadata.go

@@ -564,10 +564,7 @@ func (e *elasticsearchEngine) SearchMetadata(ctx context.Context, req *types.Sea
 		}, nil
 	}
 
-	offset := req.Offset
-	if offset < 0 {
-		offset = 0
-	}
+	offset := max(req.Offset, 0)
 	limit := req.Limit
 	if limit <= 0 {
 		limit = 30

internal/engine/infinity/chunk.go

@@ -703,10 +703,7 @@ func (e *infinityEngine) Search(ctx context.Context, req *types.SearchRequest) (
 		pageSize = 30
 	}
 
-	offset := req.Offset
-	if offset < 0 {
-		offset = 0
-	}
+	offset := max(req.Offset, 0)
 
 	db, release, err := e.client.checkoutDatabase(ctx, "chunk.go")
 	if err != nil {

internal/engine/infinity/metadata.go

@@ -583,10 +583,7 @@ func (e *infinityEngine) SearchMetadata(ctx context.Context, req *types.SearchMe
 	if pageSize <= 0 {
 		pageSize = 30
 	}
-	offset := req.Offset
-	if offset < 0 {
-		offset = 0
-	}
+	offset := max(req.Offset, 0)
 
 	// Build filter from req.Filter
 	var filterStr string