* Added `ToPyObject` and `Into<PyObject>` impls for `PyBackedStr`.
* Create 4205.added.md
* Added attributes limiting the `ToPyObject` and `IntoPy<PyObject>` impls to the case where `cfg(any(Py_3_10, not(Py_LIMITED_API)))`. When this cfg does not apply, the conversion is less trivial since the `storage` is actually `PyBytes`, not `PyString`.
* Fixed imports format.
* Updated the `ToPyObject` and `IntoPy<PyObject>` impls to support the `cfg(not(any(Py_3_10, not(Py_LIMITED_API))))` case by converting the `PyBytes` back to `PyString`.
* Added `ToPyObject` and `IntoPy<PyObject>` impls for `PyBackedBytes`.
* Added tests for the `PyBackedBytes` conversion impls.
* Updated newsfragment entry to include the `PyBackedBytes` impls.
* Changed the `IntoPy` and `ToPyObject` impls for `PyBackedBytes` to produce `PyBytes` regardless of the backing variant. Updated tests to demonstrate this.
* retrigger checks
* Updated `PyBackedStr` conversion tests to extract the result as a `PyBackedStr` instead of `&str` since the latter is not supported under some `cfg`'s.
* Fixed `IntoPy<PyObject> for PyBackedBytes` impl to create `bytes` for both storage types as intended. Updated test to properly catch the error.
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Co-authored-by: jrudolph <jrudolph@anl.gov>
