DebugTuple should have options controlling how to output tuples with 0 and 1 element.

Currently if 0 fields are provided, only the name passed into debug_tuple is printed. Would be nice if there was option to print {name}().

Currently if only 1 field is provided, trailing comma is not printed. There should be an option to add one: (value,).

These could be added as option setters on the DebugTuple builder. E.g. fn empty_tuple(bool) and fn trailing_comma(bool).

That would make debug_tuple actually usable to print tuples.