Until now, there was this magic number (64) used as the maximum number
of tasks a CPU worker can take at once.
This commit makes it a consensus parameter so our future selves can
think of a better value depending on network conditions.
Part of #40704
Signed-off-by: David Goulet <dgoulet@torproject.org>
Transform the hardcoded value ONIONQUEUE_WAIT_CUTOFF into a consensus
parameter so we can control it network wide.
Closes#40704
Signed-off-by: David Goulet <dgoulet@torproject.org>