Include changes from `importlib_metadata 3.7
<https://importlib-metadata.readthedocs.io/en/latest/history.html#v3-7-0>`_:

Performance enhancements to distribution discovery.

``entry_points`` only returns unique distributions.

Introduces new ``EntryPoints`` object
for containing a set of entry points with convenience methods for selecting
entry points by group or name.  ``entry_points`` now returns this object if
selection parameters are supplied but continues to return a dict object for
compatibility. Users are encouraged to rely on the selection interface. The
dict object result is likely to be deprecated in the future.

Added
packages_distributions function to return a mapping of packages to the
distributions that provide them.
