Merge pull request #48287 from thockin/json-iterator

Automatic merge from submit-queue

Use json-iterator instead of ugorji for JSON.

@smarterclayton @wojtek-t

Fixes #36120
xref #18762

```release-note
Switch JSON marshal/unmarshal to json-iterator library.  Performance should be close to previous with no generated code.
```

Kubernetes-commit: 6a845c67f097cd76f9d90ab3c9c5b5603c70afe4

vendor/github.com/json-iterator/go/feature_pool.go

@@ -0,0 +1,57 @@
+package jsoniter
+
+import (
+	"io"
+)
+
+// IteratorPool a thread safe pool of iterators with same configuration
+type IteratorPool interface {
+	BorrowIterator(data []byte) *Iterator
+	ReturnIterator(iter *Iterator)
+}
+
+// StreamPool a thread safe pool of streams with same configuration
+type StreamPool interface {
+	BorrowStream(writer io.Writer) *Stream
+	ReturnStream(stream *Stream)
+}
+
+func (cfg *frozenConfig) BorrowStream(writer io.Writer) *Stream {
+	select {
+	case stream := <-cfg.streamPool:
+		stream.Reset(writer)
+		return stream
+	default:
+		return NewStream(cfg, writer, 512)
+	}
+}
+
+func (cfg *frozenConfig) ReturnStream(stream *Stream) {
+	stream.Error = nil
+	select {
+	case cfg.streamPool <- stream:
+		return
+	default:
+		return
+	}
+}
+
+func (cfg *frozenConfig) BorrowIterator(data []byte) *Iterator {
+	select {
+	case iter := <-cfg.iteratorPool:
+		iter.ResetBytes(data)
+		return iter
+	default:
+		return ParseBytes(cfg, data)
+	}
+}
+
+func (cfg *frozenConfig) ReturnIterator(iter *Iterator) {
+	iter.Error = nil
+	select {
+	case cfg.iteratorPool <- iter:
+		return
+	default:
+		return
+	}
+}