[Improvement] Make codec to be a singleton. (#840)

### What changes were proposed in this pull request?
Codec will be created for many times. We should make codec to be a singleton.  I make codec to be a singleton.

### Why are the changes needed?
Fix: #389

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
  UT

Co-authored-by: tobehardest <cvchen587@163.com>

common/src/main/java/org/apache/uniffle/common/compression/Codec.java

@@ -30,14 +30,14 @@ public static Codec newInstance(RssConf rssConf) {
     Type type = rssConf.get(COMPRESSION_TYPE);
     switch (type) {
       case ZSTD:
-        return new ZstdCodec(rssConf.get(ZSTD_COMPRESSION_LEVEL));
+        return ZstdCodec.getInstance(rssConf.get(ZSTD_COMPRESSION_LEVEL));
       case SNAPPY:
-        return new SnappyCodec();
+        return SnappyCodec.getInstance();
       case NOOP:
-        return new NoOpCodec();
+        return NoOpCodec.getInstance();
       case LZ4:
       default:
-        return new Lz4Codec();
+        return Lz4Codec.getInstance();
     }
   }
 

common/src/main/java/org/apache/uniffle/common/compression/Lz4Codec.java

@@ -27,6 +27,14 @@ public class Lz4Codec extends Codec {
 
   private LZ4Factory lz4Factory;
 
+  private static class LazyHolder {
+    static final Lz4Codec INSTANCE = new Lz4Codec();
+  }
+
+  public static Lz4Codec getInstance() {
+    return LazyHolder.INSTANCE;
+  }
+
   public Lz4Codec() {
     this.lz4Factory = LZ4Factory.fastestInstance();
   }

common/src/main/java/org/apache/uniffle/common/compression/NoOpCodec.java

@@ -21,6 +21,14 @@
 
 public class NoOpCodec extends Codec {
 
+  private static class LazyHolder {
+    static final NoOpCodec INSTANCE = new NoOpCodec();
+  }
+
+  public static NoOpCodec getInstance() {
+    return LazyHolder.INSTANCE;
+  }
+
   @Override
   public void decompress(ByteBuffer src, int uncompressedLen, ByteBuffer dest, int destOffset) {
     dest.put(src);

common/src/main/java/org/apache/uniffle/common/compression/SnappyCodec.java

@@ -25,6 +25,15 @@
 import org.apache.uniffle.common.exception.RssException;
 
 public class SnappyCodec extends Codec {
+
+  private static class LazyHolder {
+    static final SnappyCodec INSTANCE = new SnappyCodec();
+  }
+
+  public static SnappyCodec getInstance() {
+    return LazyHolder.INSTANCE;
+  }
+
   @Override
   public void decompress(ByteBuffer src, int uncompressedLen, ByteBuffer dest, int destOffset) {
     try {

common/src/main/java/org/apache/uniffle/common/compression/ZstdCodec.java

@@ -28,10 +28,15 @@
 public class ZstdCodec extends Codec {
   private static final Logger LOGGER = LoggerFactory.getLogger(ZstdCodec.class);
 
-  private final int compressionLevel;
+  private int compressionLevel;
 
-  public ZstdCodec(int level) {
-    this.compressionLevel = level;
+  private static class LazyHolder {
+    static final ZstdCodec INSTANCE = new ZstdCodec();
+  }
+
+  public static ZstdCodec getInstance(int level) {
+    LazyHolder.INSTANCE.compressionLevel = level;
+    return LazyHolder.INSTANCE;
   }
 
   @Override