…t Unsafe (#16788)

Motivation:

Unpooled.wrappedBuffer(ByteBuffer) behaves differently depending on
whether Unsafe is available.

When Unsafe is enabled, wrapping a direct ByteBuffer returns a buffer
that exposes memoryAddress():

```java
  ByteBuffer byteBuffer = ByteBuffer.allocateDirect(1024);
  ByteBuf byteBuf = Unpooled.wrappedBuffer(byteBuffer);
  System.out.println(byteBuf.memoryAddress());
```

When Unsafe is disabled, the same direct ByteBuffer is wrapped by the
non-unsafe path. Even if the platform can still obtain the direct buffer
address through FFM, memoryAddress() throws
UnsupportedOperationException.

A similar inconsistency exists for the empty buffer returned by:
``` java
  ByteBuf byteBuf = ByteBufAllocator.DEFAULT.ioBuffer(0, 0);
  System.out.println(byteBuf.memoryAddress());
```

Modification:

- Use PlatformDependent.hasDirectByteBufferAddress(...) in the unpooled
direct wrapper path instead of relying only on Unsafe.
- Use the same address availability check when initializing
EmptyByteBuf's cached direct buffer address.

Result:

Fixes #<GitHub issue number>.

Unpooled wrapped direct buffers expose memoryAddress() consistently when
platform address access is available,including when Unsafe is disabled
and FFM is used

Co-authored-by: Jonas Konrad <jonas.konrad@oracle.com>
(cherry picked from commit f7b1b7d)