Aggregate progress if many progress bars are shown

[pepijndevos]

In the SciML EnsembleProblem it is possible to report progress from hundreds if not thousands of parallel simulations. This is a case that is not at all handled well by TerminalLoggers which will completely swamp the screen with jittery progress bars.

We've ended up aggregating progress messages internally, but other people chimed in as well that this is not an isolated problem. So I'd like to explore if there is interest in upstreaming the aggregation code in some form?

Possibly with some additional work to automatically aggregate after a certain number of progress bars.

SciML/SciMLBase.jl#514