minor bugs in defer_to_cancelled()

[belm0]

njs noticed a bug in early exit:

that early exit on line 84 is wrong btw... it won't notice the Cancelled in MultiError([RuntimeError, MultiError([Cancelled, Cancelled])])

trio-util/src/trio_util/_exceptions.py

Lines 84 to 85 in bd32a3e

	if not any(isinstance(exc, trio.Cancelled) for exc in exceptions):
	raise

also this function may be adding unnecessary context on exceptions:

those raise statements will automatically attach the original MultiError object as a context

could do a __context__ dance along the lines of MultiError.catch() internals

[belm0]

that early exit on line 84 is wrong btw... it won't notice the Cancelled in MultiError([RuntimeError, MultiError([Cancelled, Cancelled])])

fixed in 58db781

those raise statements will automatically attach the original MultiError object as a context

I haven't looked at this yet