[metricstarttimeprocessor] Add reset detection #38381
Description
Component(s)
processor/metricstarttime
Is your feature request related to a problem? Please describe.
The metricstarttime processor can use a variety of methods to set the start time of cumulative metrics. However, if the cumulative value of a metric ever decreases, we should treat that as a "reset" no matter the strategy that is used to ensure monotonic cumulative series never decrease.
Describe the solution you'd like
We should add reset detection, which is common to all start time strategies. This should run before other start time strategies. It should always cache the previous value for each timeseries. If it sees a value lower than the previous value, it should use the previous timestamp as the start timestamp for all subsequent points (until another reset is detected).
Describe alternatives you've considered
No response
Additional context
No response