Manage RIDs via id_alloc

kernel/proc/procgroup.h

@@ -11,6 +11,7 @@
 #include <sys/procgroup.h>
 
 #define PROCGROUP_VFS_HANDLES_MAX 256
+#define PROCGROUP_RESOURCES_MAX   256
 
 struct proc;
 struct reschedule_ctx;
@@ -29,6 +30,7 @@ struct procgroup {
   struct rb_node_link* memb_proc_tree;
   spin_lock_t lock;
   struct rb_node_link* resource_tree;
+  struct id_alloc rid_alloc;
   struct pd pd;
   struct list_node_link* mappings;
   uintptr_t map_base;