operation_parameters mutates fields

[Gavin Panella]

Fields passed into operation_parameters have their __name__ attribute
mutated.

{{{
foo = TextLine(__name__="foo")

@operation_parameters(aaa=foo)
def bar(): pass

assert foo.__name__ == "foo", foo.__name__
}}}

rename_parameters_as seems to assign to __name__ also.

Perhaps every parameter passed in should be copied first?

[Robert Collins (lifeless)]

Gavin, it would be lovely if you can triage as you file - thanks :)

[Robert Collins (lifeless)]

Triaging low for now, though this may be a dep for some functional fix we need elsewhere which would raise the importance.