Create `containers/` folder in `api/` (#4181)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4181

```
find . -type f -exec sed -i 's/api\/Tensor/api\/containers\/Tensor/g' {} +
find . -type f -exec sed -i 's/api\/ParamsBuffer/api\/containers\/ParamsBuffer/g' {} +
find . -type f -exec sed -i 's/api\/StorageBuffer/api\/containers\/StorageBuffer/g' {} +
```
ghstack-source-id: 233085712
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Reviewed By: SS-JIA

Differential Revision: D59527912

fbshipit-source-id: 09a152d42619ac649848c923c3ae7c6acf894489