[Bug]: `namespaced_function`/`alias_function` drop kwdefaults

What happened?

Having used salt.utils.functools.namespaced_function (or alias_function) to copy a function that has keyword-only arguments with defaults and calling the copy without providing a value for these yields a TypeError. Example:

from salt.utils.functools import namespaced_function, alias_function

def foo(bar=None, *_, baz=None):
    pass

foo_ns = namespaced_function(foo, globals())
foo_alias = alias_function(foo, "foo_alias")

foo()
foo_ns()
# Traceback (most recent call last):
#   File "<python-input-13>", line 1, in <module>
#     foo_ns()
#     ~~~~~~^^
# TypeError: foo() missing 1 required keyword-only argument: 'baz'
foo_alias()
# Traceback (most recent call last):
#   File "<python-input-14>", line 1, in <module>
#     foo_ns()
#     ~~~~~~^^
# TypeError: foo() missing 1 required keyword-only argument: 'baz'

Type of salt install

Official deb

Major version

3006.x

What supported OS are you seeing the problem on? Can select multiple. (If bug appears on an unsupported OS, please open a GitHub Discussion instead)

ubuntu-24.04

salt --versions-report output

Current HEAD of 3006.x

Start by reading salt.utils.functools.namespaced_function and alias_function, then reproduce the reported calls with a keyword-only default such as baz=None. Done means both copied functions retain the original keyword defaults and the regression tests pass.