Modernise GlobalTask::snooze

Snoozing a global task currently takes a double of seconds

GlobalTask::snooze(const double secs) 

and internally compares to INT_MAX, to indicate "sleep forever".

    if (secs == INT_MAX) {

        setState(TASK_SNOOZED, TASK_RUNNING);

        updateWaketime(std::chrono::steady_clock::time_point::max());

        return;

    }

Therefore, many callers provide INT_MAX or std::numeric_limits<int>::max(), which is converted to a double, then compared against an int.

This leaves the possibility of typos (e.g., UINT_MAX, std::numeric_limits<size_t>::max()), and requires the caller to handle the units (seconds vs milliseconds etc).

The interface could be improved with by taking a duration, e.g.,

GlobalTask::snooze(std::chrono::steady_clock::duration sleepTime)