Remove PersistenceBenchmark

[Aaronontheweb]

Our Akka.Persistence benchmarks are pretty ancient https://github.com/akkadotnet/akka.net/blob/dev/src/benchmark/PersistenceBenchmark/Program.cs

I'll see about adding some BenchmarkDotNet ones.

Originally posted by @Aaronontheweb in #5505 (comment)

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We should delete the PersistenceBenchmark - byte rotted and we'd prefer a BenchmarkDotNet solution here.

[Aaronontheweb]

Still have to remove the old benchmarks even if we have a decent replacement for them now

[dengia]

Hi @Aaronontheweb, I went through benchmarks:
PersistentBenchamarks --> Akka.Cluster.Benchmarks/Persistence
PingPong --> Akka.Benchmarks/Actor/PingPongBenchmarks.cs
SerializationBenchmarks --> Akka.Benchmarks/Actor/Serialization
RemotePingPong --> ?
SpawnBenchmark --> ?
Question: is this correct? If yes, shall I remove those three old benchmarks with decent replacement?

[Aaronontheweb]

@dengia those benchmarks are fine, it's just this folder that needs to be deleted https://github.com/akkadotnet/akka.net/tree/dev/src/benchmark/PersistenceBenchmark