fix(runtime): enable concurrent key usage by cloning it on get operation.

compiler/lib/Runtime/context.c

@@ -1,3 +1,4 @@
+#include "concrete-ffi.h"
 #include "zamalang/Runtime/context.h"
 #include <stdio.h>
 
@@ -6,5 +7,10 @@ LweKeyswitchKey_u64 *get_keyswitch_key(RuntimeContext *context) {
 }
 
 LweBootstrapKey_u64 *get_bootstrap_key(RuntimeContext *context) {
-  return context->bsk;
+  int err;
+  LweBootstrapKey_u64 *clone =
+    clone_lwe_bootstrap_key_u64(&err, context->bsk);
+  if (err != 0)
+    fprintf(stderr, "Runtime: cloning bootstrap key failed.\n");
+  return clone;
 }