link: remove `FnData` and make it self-owned

This finishes the work started in #14502 where atoms are owned by the
linker themselves. This now makes debug atoms fully owned by dwarf,
and no information is left stored on the decl.
c9b957c937Luuk de Gram committed on 2/3/2023, 9:55:46 PM· committed by Jakub Konkaparent60935de
3 files changedLine totals unavailable