Support showing metrics as deltas

For metrics that count things (bytes, exceptions, connections, events, etc), the delta of the metric per time interval may be more telling than the current value. This is especially true for frequently changing values, where the rate of change is interesting.

Another way of thinking about this is as taking the derivative of the chart.

We should support toggling a chart/table between value/delta. The table view already has an option:


We can add a new option to "Show deltas".

Per https://github.com/dotnet/aspire/issues/5287 we would move this option to a menu when the chart is used in a dashpage.