Check global state destruction in destructors

In some cases the global state may have been destroyed when we reach
`umfDestroyPool` or `umfDestroyProvider`, in which case actually going
through with the destruction will cause segmentation faults.

The way the global state is managed should maybe be re-worked, but this
should be an okay workaround to avoid segmentation faults until then.

Author: npmiller

src/memory_pool.c

@@ -85,6 +85,10 @@ static umf_result_t umfPoolCreateInternal(const umf_memory_pool_ops_t *ops,
 }
 
 void umfPoolDestroy(umf_memory_pool_handle_t hPool) {
+    if (umf_ba_global_is_destroyed()) {
+        return;
+    }
+
     hPool->ops.finalize(hPool->pool_priv);
 
     umf_memory_provider_handle_t hUpstreamProvider = NULL;

src/memory_provider.c

@@ -194,7 +194,7 @@ umf_result_t umfMemoryProviderCreate(const umf_memory_provider_ops_t *ops,
 }
 
 void umfMemoryProviderDestroy(umf_memory_provider_handle_t hProvider) {
-    if (hProvider) {
+    if (hProvider && !umf_ba_global_is_destroyed()) {
         hProvider->ops.finalize(hProvider->provider_priv);
         umf_ba_global_free(hProvider);
     }