Add `dict` methods to `ParameterDict` (#69403)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/68476
We implemented all of the following `dict` methods for `ParameterDict`
- `get `
- `setdefault`
- `popitem`
- `fromkeys`
- `copy`
- `__or__`
- `__ior__`
- `__reversed__`
- `__ror__`
The behavior of these new methods matches the expected behavior of python `dict` as defined by the language itself: https://docs.python.org/3/library/stdtypes.html#typesmapping
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69403
Reviewed By: albanD
Differential Revision: D33187111
Pulled By: jbschlosser
fbshipit-source-id: ecaa493837dbc9d8566ddbb113b898997e2debcb
