[Feature]: Ability to override/provide time_unix_nano whenm creating metric

[REASY]

Related Problems?

No response

Describe the solution you'd like:

I would want to have a way to assing time/start_time of a metric so I have a better control over it, instead of using SystemTime::now

pub(crate) struct AggregateTimeInitiator(Mutex<SystemTime>);

impl AggregateTimeInitiator {
    pub(crate) fn delta(&self) -> AggregateTime {
        let current_time = SystemTime::now();
        let start_time = self
            .0
            .lock()
            .map(|mut start| replace(start.deref_mut(), current_time))
            .unwrap_or(current_time);
        AggregateTime {
            start: start_time,
            current: current_time,
        }
    }

    pub(crate) fn cumulative(&self) -> AggregateTime {
        let current_time = SystemTime::now();
        let start_time = self.0.lock().map(|start| *start).unwrap_or(current_time);
        AggregateTime {
            start: start_time,
            current: current_time,
        }
    }
}

Considered Alternatives

No response

Additional Context

No response