vote: Move dirvote_recalculate_timing() to voting_schedule.c

By doing so, it is renamed to voting_schedule_recalculate_timing(). This
required a lot of changes to include voting_schedule.h everywhere that this
function was used.

This effectively now makes voting_schedule.{c|h} not include dirauth/dirvote.h
for that symbol and thus no dependency on the dirauth module anymore.

Signed-off-by: David Goulet <dgoulet@torproject.org>