`rb_ractor_thread_list()` only for current ractor

so that no need to lock the ractor.

ractor.c

@@ -2120,34 +2120,23 @@ rb_ractor_living_thread_num(const rb_ractor_t *r)
     return r->threads.cnt;
 }
 
+// only for current ractor
 VALUE
-rb_ractor_thread_list(rb_ractor_t *r)
+rb_ractor_thread_list(void)
 {
+    rb_ractor_t *r = GET_RACTOR();
     rb_thread_t *th = 0;
-    VALUE *ts;
-    int ts_cnt;
-
-    RACTOR_LOCK(r);
-    {
-        ts = ALLOCA_N(VALUE, r->threads.cnt);
-        ts_cnt = 0;
-
-        ccan_list_for_each(&r->threads.set, th, lt_node) {
-            switch (th->status) {
-              case THREAD_RUNNABLE:
-              case THREAD_STOPPED:
-              case THREAD_STOPPED_FOREVER:
-                ts[ts_cnt++] = th->self;
-              default:
-                break;
-            }
-        }
-    }
-    RACTOR_UNLOCK(r);
-
     VALUE ary = rb_ary_new();
-    for (int i=0; i<ts_cnt; i++) {
-        rb_ary_push(ary, ts[i]);
+
+    ccan_list_for_each(&r->threads.set, th, lt_node) {
+        switch (th->status) {
+          case THREAD_RUNNABLE:
+          case THREAD_STOPPED:
+          case THREAD_STOPPED_FOREVER:
+            rb_ary_push(ary, th->self);
+          default:
+            break;
+        }
     }
 
     return ary;

ractor_core.h

@@ -209,7 +209,7 @@ void rb_ractor_send_parameters(rb_execution_context_t *ec, rb_ractor_t *g, VALUE
 VALUE rb_thread_create_ractor(rb_ractor_t *g, VALUE args, VALUE proc); // defined in thread.c
 
 int rb_ractor_living_thread_num(const rb_ractor_t *);
-VALUE rb_ractor_thread_list(rb_ractor_t *r);
+VALUE rb_ractor_thread_list(void);
 bool rb_ractor_p(VALUE rv);
 
 void rb_ractor_living_threads_init(rb_ractor_t *r);

thread.c

@@ -2728,7 +2728,7 @@ VALUE
 rb_thread_list(void)
 {
     // TODO
-    return rb_ractor_thread_list(GET_RACTOR());
+    return rb_ractor_thread_list();
 }
 
 /*