Guarantee DedicatedThreadScheduler clean shutdowns #2288
Description
Need to guarantee that the scheduler is always properly disposed of whenever the ActorSystem terminates. This is currently blocking our ability to run CI on Mono as we run into these sorts of exceptions when running larger test suites:
System.SystemException : Thread creation failed.
at System.Threading.Thread.StartInternal (IPrincipal principal, System.Threading.StackCrawlMark& stackMark) <0x411f1470 + 0x000e7> in <filename unknown>:0
at System.Threading.Thread.Start (System.Threading.StackCrawlMark& stackMark) <0x411f1320 + 0x000c4> in <filename unknown>:0
at System.Threading.Thread.Start () <0x412bb920 + 0x0002b> in <filename unknown>:0
at Akka.Actor.DedicatedThreadScheduler..ctor (Akka.Actor.ActorSystem system) <0x412bb410 + 0x002e3> in <filename unknown>:0
at (wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke (System.Reflection.MonoCMethod,object,object[],System.Exception&)
at System.Reflection.MonoCMethod.InternalInvoke (System.Object obj, System.Object[] parameters) <0x411618d0 + 0x00045> in <filename unknown>:0