[processor/cumulativetodelta] Support persistant storage.

[h0cheung]

Component(s)

processor/cumulativetodelta

Is your feature request related to a problem? Please describe.

When the collector is restarted and the last point before the restart does not exist, the delta value cannot be calculated for the new first point, it can only be discarded. This causes a breakpoint, and the total for the period is calculated to be lower than the true value.

Describe the solution you'd like

Support persistent storage. This way the collector could get the last value to calculate the delta value after restarting.

Describe alternatives you've considered

No response

Additional context

No response