This commit changes how we transform from a deadline option to a
concrete deadline value - previously this is done when we decide to
cluster inputs, and we now move it to a step earlier - once an input is
received via `SweeperInput`, we will immediately transform its optional
deadline into a real value. For inputs that come with a deadline option,
since the Some will be used, it makes no difference. For inputs with
None as their deadlines, we need this change to make sure the default
deadlines are assigned accurately.
yyforyongyu
a50cdd64c5