ipf: copy{in,out}ptr -> ipf_copy{in,out}_indirect

These functions take the source or destintation address indirectly from
a potentially missaligned buffer. Rename them to refect this and to
free up the copy{in,out}ptr names.

Some of the code in question is dead code and doesn't or won't compile,
but I've changed it all for consistency.

NB: If the pointers are actually stored under aligned then this code is
broken with CHERI.

Reviewed by: cy
Effort: CHERI upstreaming
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D54232