[bf16] support printing bf16 tensor

[zhiqiu]

PR types

New features

PR changes

APIs

Describe

Related #39370

For example, bf16 tensor with data [[1,5, 1],[0, 0]]

• before

Tensor(shape=[2, 2], dtype=uint16, place=Place(gpu:0), stop_gradient=True,
       [[16320, 16256],
        [0    , 0    ]])

• after

Tensor(shape=[2, 2], dtype=bfloat16, place=Place(gpu:0), stop_gradient=True,
       [[1.50000000, 1.        ],
        [0.        , 0.        ]])

[paddle-bot-old]

Thanks for your contribution!
Please wait for the result of CI firstly. See Paddle CI Manual for details.

[zhangbo9674]

LGTM