* deprecate the use of `PyCell` in favor of `Bound` and `Py`
* update `FromPyObject` for `T: PyClass + Clone` impl
* move `PyCell` deprecation to the `gil-refs` feature gate and add a migration note
* deprecate `PyCell::new` in favor of `Py::new` or `Bound::new`
* update deprecation warning
Co-authored-by: David Hewitt <mail@davidhewitt.dev>
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Co-authored-by: David Hewitt <mail@davidhewitt.dev>
* Use the new bound API instead of .as_ref(py)
* Move import into a nested scope
* Use to_cow instead of to_str for compatibility
`to_str` is not available before Python 3.10 on the limited api.
* Relax &self lifetimes
* Use Bound<'py, PyAny> in test Mapping signatures
* Use .as_bytes(py)
* Simplify ThrowCallback::throw signature
* Avoid .as_any call with Py api instead of Bound