- BREAKING replace loadavg and system check from millis to seconds
- implement all available system clocks, make sure it is correctly
scaled with the origin type
- fix duration::{millis(),ccount(),seconds()} and return a respective
clock's time_point instead of duration. just like led sources, make
sure every module stores timestamps as time_point and intervals as
duration
- no need to track millis overflow on top of existing overflow counter
of the micros64 in getUptime
- remove class overhead in led static delays conversion, just try to
inline the required calculations and use NAME as unique id
also fix some non-apparent issues with heartbeat
- allow zero interval when it is also Mode::Once
- iterating runners to find the interval might return zero