Add list helpers to support task state transition

Previously, list_pushback() and list_remove() were the only list APIs
available for data insertion into and removal from the list by malloc
a new and free target linkage node.

After the new data structure, rq_node, is added as the linkage node
for ready queue operation purpose, there is no need to malloc and
free each time.

Add the insertion and removal list helpers without malloc and free
on the linkage node. Both APIs will be applied in the dequeue and
enqueue paths.

Author: vicLin8712

include/lib/list.h

@@ -100,6 +100,24 @@ static inline list_node_t *list_pushback(list_t *list, void *data)
     return node;
 }
 
+/* Pushback list node into list */
+static inline void list_pushback_node(list_t *list, list_node_t *target)
+{
+    if (unlikely(!list || !target || target->next))
+        return;
+
+    target->next = list->tail;
+
+    /* Insert before tail sentinel */
+    list_node_t *prev = list->head;
+    while (prev->next != list->tail)
+        prev = prev->next;
+
+    prev->next = target;
+    list->length++;
+    return;
+}
+
 static inline void *list_pop(list_t *list)
 {
     if (unlikely(list_is_empty(list)))
@@ -134,6 +152,25 @@ static inline void *list_remove(list_t *list, list_node_t *target)
     return data;
 }
 
+/* Remove a node from list without freeing */
+static inline void list_remove_node(list_t *list, list_node_t *target)
+{
+    if (unlikely(!list || !target || list_is_empty(list)))
+        return;
+
+    list_node_t *prev = list->head;
+    while (prev->next != list->tail && prev->next != target)
+        prev = prev->next;
+
+    if (unlikely(prev->next != target))
+        return; /* node not found */
+
+    prev->next = target->next;
+    target->next = NULL;
+    list->length--;
+    return;
+}
+
 /* Iteration */
 
 /* Callback should return non-NULL to stop early, NULL to continue */