funcutils.wraps drops positional-only parameters from generated signatures

funcutils.wraps drops the / marker when compiling a wrapper, so a positional-only parameter becomes positional-or-keyword. This breaks valid calls that reuse the parameter name inside **kwargs.

Reproduced on upstream master at 961dcff3f42e73b245aef65e377fe82763b257bb:

from boltons.funcutils import wraps

def original(a, /, **kw):
    return a, kw

@wraps(original)
def wrapped(*args, **kwargs):
    return original(*args, **kwargs)

print(original(1, a=2))  # (1, {'a': 2})
print(wrapped(1, a=2))   # TypeError: original() got multiple values for argument 'a'

The wrapped call should return the same result as the original. Its generated source is currently:

def original(a, **kw):
    return _call(a, **kw)

FunctionBuilder.from_func(original) records posonlyargs == ['a'], but get_sig_str() does not pass that information to the signature formatter. The argument collision happens before the wrapper body runs. The existing positional-only regression checks forwarding of positional calls and does not cover this collision.

#425 and #445 address argument forwarding; this concerns the generated function's calling signature.

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