Fix initialization for missing parameters in `from_pretrained` under ZeRO-3
Author: XuehaiPan
Pull request: yes

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This PR adds `deepspeed.zero.GatheredParameters` context during initialization of the missing parameters. These parameters are already partitioned, so their sizes are `torch.Size([])`. The `torch.nn.init.func_()` functions will have no effect on these parameters. This PR gathers the parameters before initialization and repartition them after initialization.

Fixes #28244

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Comments:
I add a simple test case in this PR. I also test it with and without the patch in this PR:

- with the patch: PASS
- without the patch (main branch): FAIL

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