[Formatter] Javadoc formatter sometimes incorrectly encodes `@` to `@` inside {@code} blocks

The formatter incorrectly encodes certain `@` symbols that are included in `

 {@code` javadoc blocks. I am not sure the rules for encoding the `@` on annotations, it doesn't appear to break anything but encoding it on a `{@code` does break the javadoc rendering.


Possibly related to: https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2071

Reproduction Input:

```

  /**

   * Example showing formatter bug with {@code @} in pre blocks.

   *

   * 
   * {@code

   * @MyAnnotation

   * public class Example {

   *

   *     @AnotherAnnotation

   *     private String field;

   * }

   * }

   * 

   */

  public interface ExampleService {


      /**

       * Another method with annotation in javadoc.

       *

       * 
       * {@code

       * @Override

       * public void doSomething() {

       *     // implementation

       * }

       * }

       * 

       */

      void doSomething();

  }

```


---  

With "Enable Classic Javadoc formatting" : False

With "Format Java code snippets inside 'pre' tags": False

Result: No Change

---

With "Enable Classic Javadoc formatting" : True

With "Format Java code snippets inside 'pre' tags": False

Result: `@`'s on some Annotations are converted to `@`

```

/**

 * Example showing formatter bug with {@code @} in pre blocks.

 *

 * 
 * {@code

 * @MyAnnotation     <--- Possible error

 * public class Example {

 *

 *     @AnotherAnnotation    <--- Why did this not get encoded

 *     private String field;

 * }

 * }

 * 

 */

public interface ExampleService {

	/**

	 * Another method with annotation in javadoc.

	 *

	 * 
	 * {@code

	 * @Override    <--- Possible error

	 * public void doSomething() {

	 *     // implementation

	 * }

	 * }

	 * 

	 */

	void doSomething();

}

```

---


With "Enable Classic Javadoc formatting" : True

With "Format Java code snippets inside 'pre' tags": True

Result: `@`'s on some Annotations _and_ some `{@code` are converted to `@`

```

/**

 * Example showing formatter bug with {@code @} in pre blocks.

 *

 * 
 * {

 * 	@code    <--- Definitive error

 * 	@MyAnnotation

 * 	public class Example {

 * 		@AnotherAnnotation

 * 		private String field;

 * 	}

 * }

 * 

 */

public interface ExampleService {

	/**

	 * Another method with annotation in javadoc.

	 *

	 * 
	 * {@code

	 * @Override

	 * public void doSomething() {

	 * 	// implementation

	 * }

	 * }

	 * 

	 */

	void doSomething();

}

```