[Cherry-Pick][Dy2St]Support call backward() without params in dy2st (#49812)#50144

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phlrain merged 3 commits intoPaddlePaddle:release/2.4from

0x45f:cherry-dy2st-backward-without-params

Feb 3, 2023

Commits on Feb 1, 2023

[Dy2St]Support call backward() without params in dy2st (#49812)

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