goto-char as the last thing in a save-excursion is never right
Refactor do-prepend-insert, do-append-insert, and do-insert into one function

791330f7 did some simplification, which was later improved upon by
88077ef4, to browse-kill-ring-do-insert. Sibling functions
browse-kill-ring-do-prepend-insert and
browse-kill-ring-do-append-insert were left untouched. Since these
functions are basically just copies of each other, refactor the shared
parts into a shared function, browse-kill-ring-insert-and-highlight.