Extract SdkByteArrayOutputStream and GC optimizations to separate branch

Remove optimizations 3 (SdkByteArrayOutputStream for G1GC humongous
allocation avoidance) and 4 (contentStreamProvider/contentSize zero-copy
streaming) from this branch. These will be reviewed separately on
alexwoo/json_huge_gc_opt.

This branch now contains only:
- Optimization 1: Megamorphic interface dispatch fix (switch-based
  marshallPayloadField)
- Optimization 2: Redundant registry lookup caching
  (marshallFieldViaRegistry with ConcurrentHashMap cache)
- writeBinaryValue addition (used by SDK_BYTES switch case)

Author: alextwoods

core/protocols/aws-json-protocol/src/main/java/software/amazon/awssdk/protocols/json/SdkByteArrayOutputStream.java

@@ -15,14 +15,14 @@
 
 package software.amazon.awssdk.protocols.json;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
 import java.time.Instant;
 import software.amazon.awssdk.annotations.SdkProtectedApi;
 import software.amazon.awssdk.core.exception.SdkClientException;
-import software.amazon.awssdk.http.ContentStreamProvider;
 import software.amazon.awssdk.thirdparty.jackson.core.JsonFactory;
 import software.amazon.awssdk.thirdparty.jackson.core.JsonGenerator;
 import software.amazon.awssdk.utils.BinaryUtils;
@@ -39,7 +39,7 @@ public class SdkJsonGenerator implements StructuredJsonGenerator {
      * prevent frequent resizings but small enough to avoid wasted allocations for small requests.
      */
     private static final int DEFAULT_BUFFER_SIZE = 1024;
-    private final SdkByteArrayOutputStream baos = new SdkByteArrayOutputStream(DEFAULT_BUFFER_SIZE);
+    private final ByteArrayOutputStream baos = new ByteArrayOutputStream(DEFAULT_BUFFER_SIZE);
     private final JsonGenerator generator;
     private final String contentType;
 
@@ -287,24 +287,6 @@ public byte[] getBytes() {
         return baos.toByteArray();
     }
 
-    /**
-     * Returns the size of the generated content in bytes without copying.
-     */
-    public int contentSize() {
-        close();
-        return baos.contentSize();
-    }
-
-    /**
-     * Returns a {@link ContentStreamProvider} that streams directly from the internal buffers
-     * without creating a contiguous copy. For small payloads this wraps the single base buffer;
-     * for large payloads it chains the base buffer and overflow chunks.
-     */
-    public ContentStreamProvider contentStreamProvider() {
-        close();
-        return baos.contentStreamProvider();
-    }
-
     @Override
     public String getContentType() {
         return contentType;

core/protocols/aws-json-protocol/src/main/java/software/amazon/awssdk/protocols/json/SdkJsonGenerator.java

@@ -15,13 +15,11 @@
 
 package software.amazon.awssdk.protocols.json;
 
-import java.io.ByteArrayInputStream;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
 import java.time.Instant;
 import software.amazon.awssdk.annotations.SdkProtectedApi;
-import software.amazon.awssdk.http.ContentStreamProvider;
 
 /**
  * Interface for generating a JSON
@@ -200,28 +198,4 @@ default StructuredJsonGenerator writeBinaryValue(byte[] bytes) {
      */
     @Deprecated
     String getContentType();
-
-    /**
-     * Returns the size of the generated content in bytes without copying. The default
-     * implementation falls back to {@link #getBytes()}.length.
-     */
-    default int contentSize() {
-        byte[] bytes = getBytes();
-        return bytes == null ? 0 : bytes.length;
-    }
-
-    /**
-     * Returns a {@link ContentStreamProvider} that streams the generated content. The default
-     * implementation wraps the result of {@link #getBytes()} in a {@code ByteArrayInputStream}.
-     * Implementations may override this to stream directly from internal buffers without copying.
-     *
-     * @return a content stream provider, or {@code null} if {@link #getBytes()} returns null
-     */
-    default ContentStreamProvider contentStreamProvider() {
-        byte[] bytes = getBytes();
-        if (bytes == null) {
-            return null;
-        }
-        return () -> new ByteArrayInputStream(bytes);
-    }
 }

core/protocols/aws-json-protocol/src/main/java/software/amazon/awssdk/protocols/json/StructuredJsonGenerator.java

@@ -43,7 +43,6 @@
 import software.amazon.awssdk.core.traits.RequiredTrait;
 import software.amazon.awssdk.core.traits.TimestampFormatTrait;
 import software.amazon.awssdk.core.traits.TraitType;
-import software.amazon.awssdk.http.ContentStreamProvider;
 import software.amazon.awssdk.http.SdkHttpFullRequest;
 import software.amazon.awssdk.protocols.core.InstantToString;
 import software.amazon.awssdk.protocols.core.OperationInfo;
@@ -291,12 +290,12 @@ private SdkHttpFullRequest finishMarshalling() {
                 jsonGenerator.writeEndObject();
             }
 
-            ContentStreamProvider contentProvider = jsonGenerator.contentStreamProvider();
-            if (contentProvider != null) {
-                request.contentStreamProvider(contentProvider);
-                int contentSize = jsonGenerator.contentSize();
-                if (contentSize > 0) {
-                    request.putHeader(CONTENT_LENGTH, Integer.toString(contentSize));
+            byte[] content = jsonGenerator.getBytes();
+
+            if (content != null) {
+                request.contentStreamProvider(() -> new ByteArrayInputStream(content));
+                if (content.length > 0) {
+                    request.putHeader(CONTENT_LENGTH, Integer.toString(content.length));
                 }
             }
         }