Add support for Cooperative Suspend when running on Mono

Informs mono runtime that Job System, Thread Pool or Content Load threads can wait when they are going idle between tasks.

Source/Engine/Threading/JobSystem.cpp

@@ -15,6 +15,7 @@
 #include "Engine/Profiler/ProfilerMemory.h"
 #if USE_CSHARP
 #include "Engine/Scripting/ManagedCLR/MCore.h"
+#include "Engine/Scripting/Internal/InternalCalls.h"
 #endif
 
 #define JOB_SYSTEM_ENABLED 1
@@ -184,6 +185,7 @@ int32 JobSystemThread::Run()
     JobData data;
     Function<void(int32)> job;
     bool attachCSharpThread = true;
+    MONO_THREAD_INFO_TYPE* monoThreadInfo = nullptr;
     while (Platform::AtomicRead(&ExitFlag) == 0)
     {
         // Try to get a job
@@ -205,6 +207,7 @@ int32 JobSystemThread::Run()
             {
                 MCore::Thread::Attach();
                 attachCSharpThread = false;
+                monoThreadInfo = mono_thread_info_attach();
             }
 #endif
 
@@ -244,9 +247,11 @@ int32 JobSystemThread::Run()
         else
         {
             // Wait for signal
+            MONO_ENTER_GC_SAFE_WITH_INFO(monoThreadInfo);
             JobsMutex.Lock();
             JobsSignal.Wait(JobsMutex);
             JobsMutex.Unlock();
+            MONO_EXIT_GC_SAFE_WITH_INFO;
         }
     }
     return 0;