Introduces Bytes class (#1019)

This introduces a new `Bytes` standard library class, for working with
binary data.

* Add Bytes class to the standard library
* Change CLI to eval `output.bytes`
* Change code generators to map Bytes to respective underlying type
* Add subscript and concat operator support
* Add binary encoding for Bytes
* Add PCF and Plist rendering for Bytes

Co-authored-by: Kushal Pisavadia <kushi.p@gmail.com>

pkl-config-java/src/test/java/org/pkl/config/java/mapper/BytesToByteArrayTest.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.pkl.config.java.mapper;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.pkl.core.ModuleSource.modulePath;
+
+import org.junit.jupiter.api.Test;
+import org.pkl.core.Evaluator;
+import org.pkl.core.PModule;
+
+public class BytesToByteArrayTest {
+  private static final Evaluator evaluator = Evaluator.preconfigured();
+
+  private static final PModule module =
+      evaluator.evaluate(modulePath("org/pkl/config/java/mapper/BytesToByteArrayTest.pkl"));
+
+  private static final ValueMapper mapper = ValueMapperBuilder.preconfigured().build();
+
+  @Test
+  public void ex1() {
+    var ex1 = module.getProperty("ex1");
+    var mapped = mapper.map(ex1, Types.arrayOf(byte.class));
+    assertThat(mapped).isEqualTo(new byte[] {});
+  }
+
+  @Test
+  public void ex2() {
+    var ex2 = module.getProperty("ex2");
+    var mapped = mapper.map(ex2, Types.arrayOf(byte.class));
+    assertThat(mapped).isEqualTo(new byte[] {1, 2, 3, 4});
+  }
+}

pkl-config-java/src/test/resources/org/pkl/config/java/mapper/BytesToByteArrayTest.pkl

@@ -0,0 +1,2 @@
+ex1 = Bytes()
+ex2 = Bytes(1, 2, 3, 4)