Set a max-history-duration for Diagnostics

## What problem does this solve or what need does it fill?

I feel like with diagnostics, the value I often want to know is:
'what was the average value over the last X seconds'
(for example what was the bandwidth over the last 1 second, or what was the fps averaged over the last 3 seconds).

The current diagnostics requires you to specify a `max_history_length` which will be the number of values stored in the buffer.
But personally I don't particulary care for the 'bandwidth over the last 64 measurements`, i'm more interested in knowing in knowing the value averaged over a specific amount of time.

## What solution would you like?

The API could accept a parameter like
```
pub enum HistorySize {
HistoryLength(u32),
HistoryDuration(Duration)
}
```

Start by locating the Diagnostics API and the existing max_history_length configuration. Compare the proposed HistorySize enum with current history handling, then verify that duration-based history can produce averages over intervals such as one or three seconds while preserving length-based behavior.

Written by the indexing model from the issue text.