header/footer macros $F and $f show bogus information for linked parts

Using the $F macro in linked parts' headers/footers results in a bogus string, a filename that doesn't exist.
The macro $f has a similar issue.

Possible (and IMHO most sensible) solution: use the rootfile's name instead

Related: the $M and $m macros's results are empty on linked parts, see #34421: need a macro for 'last modified' in header/footer