Disable aux stack allocations for threads spawned by wasi_thread_start (#1867)

This syscall doesn't need allocating stack or TLS and it's expected from the application
to do that instead. E.g. WASI-libc already does this for `pthread_create`.

Also fix some of the examples to allocate memory for stack and not use stack before
the stack pointer is set to a correct value.

core/iwasm/common/wasm_exec_env.h

@@ -179,6 +179,13 @@ wasm_exec_env_create(struct WASMModuleInstanceCommon *module_inst,
 void
 wasm_exec_env_destroy(WASMExecEnv *exec_env);
 
+static inline bool
+wasm_exec_env_is_aux_stack_managed_by_runtime(WASMExecEnv *exec_env)
+{
+    return exec_env->aux_stack_boundary.boundary != 0
+           || exec_env->aux_stack_bottom.bottom != 0;
+}
+
 /**
  * Allocate a WASM frame from the WASM stack.
  *