Simplify block_find_symbol

Simplify block_find_symbol

block_find_symbol takes a callback function, but only two callbacks
are ever passed to it -- and they are similar enough that it seems
cleaner to just have block_find_symbol do the work itself.  Also,
block_find_symbol can take a lookup_name_info as an argument,
following the general idea of pushing the construction of these
objects as high in the call chain as feasible.

Regression tested on x86-64 Fedora 38.

Tested-By: Alexandra Petlanova Hajkova <ahajkova@redhat.com>