Initialize the rng of external threads (#47956)

* Initialize the rng of external threads with uv_random

(cherry picked from commit 4c2a431)

src/threading.c

@@ -408,7 +408,7 @@ JL_DLLEXPORT jl_gcframe_t **jl_adopt_thread(void)
     // warning: this changes `jl_current_task`, so be careful not to call that from this function
     jl_task_t *ct = jl_init_root_task(ptls, stack_lo, stack_hi);
     JL_GC_PROMISE_ROOTED(ct);
-
+    uv_random(NULL, NULL, &ct->rngState, sizeof(ct->rngState), 0, NULL);
     return &ct->gcstack;
 }