gguf-py : fix passing non-native endian tensors (editor-gui and new-metadata) (#17553)

gguf_new_metadata.py reads data from reader.
Reader doesn't byteswap tensors to native endianness.
But writer does expect tensors in native endianness to convert them
into requested endianness.

There are two ways to fix this: update reader and do conversion to native endianness and back,
or skip converting endianness in writer in this particular USE-case.

gguf_editor_gui.py doesn't allow editing or viewing tensor data.
Let's go with skipping excessive byteswapping.

If eventually capability to view or edit tensor data is added,
tensor data should be instead byteswapped when reading it.

gguf-py/gguf/scripts/gguf_new_metadata.py

@@ -94,7 +94,7 @@ def copy_with_new_metadata(reader: gguf.GGUFReader, writer: gguf.GGUFWriter, new
     writer.write_ti_data_to_file()
 
     for tensor in reader.tensors:
-        writer.write_tensor_data(tensor.data)
+        writer.write_tensor_data(tensor.data, tensor_endianess=reader.endianess)
         bar.update(tensor.n_bytes)
 
     writer.close()