Add EventSource logging to RateLimitingMiddleware

[wtgodbe]

Follow-up to #41008, part of #37384. See https://github.com/dotnet/aspnetcore/blob/main/docs/EventSourceAndCounters.md. Should give info about what fired a given acceptance/rejection, and perhaps do counters here too. Related to #44140

[davidfowl]

What are we adding? Can we list the events and counters here? I wonder if we should switch to metrics in .NET 7?

cc @noahfalk

[adityamandaleeka]

@wtgodbe Do we have a set of things we want to add for this? Will it happen in preview6?

[wtgodbe]

Not yet - I'm planning to do it in the endpoint PR, unless that would put that PR at risk of missing preview6. In that case I'd do it in a separate PR for preview7