Add SignalR Native AOT benchmarks

[eerhardt]

.NET 9 added support for native AOT'ing SignalR. We should add a scenario to our benchmarks.

The current thinking is to reuse the SignalR scenario:

• json protocol
• websockets
• Either echo or echoAll

And put the results in the "nativeAOT" benchmark table.

We can run this scenario against:

• coreclr
• nativeAOT
• TrimR2RSingleFile