Implement suspend flags as atomic variable (#2361)

We have observed a significant performance degradation after merging
https://github.com/bytecodealliance/wasm-micro-runtime/pull/1991
Instead of protecting suspend flags with a mutex, we implement the flags
as atomic variable and only use mutex when atomics are not available
on a given platform.

core/shared/utils/bh_platform.h

@@ -16,6 +16,7 @@
 #include "bh_log.h"
 #include "bh_queue.h"
 #include "bh_vector.h"
+#include "gnuc.h"
 #include "runtime_timer.h"
 
 /**