Add __get__ to the partial object

Feature or enhancement

In #119827 (comment), @rhettinger proposed to add the __get__ method to the partial object in functools. This is a breaking change, although the impact may be much lesser than of adding __get__ to builtin functions. But we should follow the common procedure for such changes: first add __get__ that emits FutureWarning with suggestion to wrap partial into staticmethod and return the partial object unchanged, then change the behavior few releases later.

Linked PRs

• gh-121027: Add a future warning in functools.partial.__get__ #121086
• gh-121027: Make the functools.partial object a method descriptor #121089
• [3.13] gh-121027: Add a future warning in functools.partial.__get__ (GH-121086) #121092