[caffe2] Add support for std::shared_ptr<std::vector<TensorList>> in PackRecordsOp and UnPackRecordsOp (#36550)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36550
Separate dataset_ops changes into a separate diff.
Test Plan:
```
buck test caffe2/caffe2/python/operator_test:dataset_ops_test
```
AI/AF canary (tested with D20959214):
https://our.intern.facebook.com/intern/experiment_store/experiment/3298538636995/#commit1-commit2
https://our.intern.facebook.com/intern/experiment_store/experiment/2199027015376/#commit1-commit2
Reviewed By: yinghai
Differential Revision: D20988910
fbshipit-source-id: b37a7bfd131813e9472a5e2fa24d681d1ef19018
