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/Scripting/Runtime/DotNet.cpp

@@ -2147,7 +2147,13 @@ bool InitHostfxr()
 #endif
 
     // Adjust GC threads suspending mode to not block attached native threads (eg. Job System)
+    // https://www.mono-project.com/docs/advanced/runtime/docs/coop-suspend/
+#if USE_MONO_AOT_COOP
+    Platform::SetEnvironmentVariable(TEXT("MONO_THREADS_SUSPEND"), TEXT("coop"));
+    Platform::SetEnvironmentVariable(TEXT("MONO_SLEEP_ABORT_LIMIT"), TEXT("5000")); // in ms
+#else
     Platform::SetEnvironmentVariable(TEXT("MONO_THREADS_SUSPEND"), TEXT("preemptive"));
+#endif
 
 #if defined(USE_MONO_AOT_MODE)
     // Enable AOT mode (per-platform)