9830: Enable more assists to generate default trait body impls r=Veykril a=yoshuawuyts
Enable more assists to benefit from trait body generation. Follow-up to #9825 and #9814.
__edit:__ I'd like to move the existing tests to this new file too, but I'll do that in a follow-up PR.
Co-authored-by: Yoshua Wuyts <yoshuawuyts@gmail.com>
e652545472