[smart] split out part of lwp_new() to lwp_create()

Prev implementation of lwp_new() including the create of lwp object
and the pid allocation. But not every lwp object need a pid.
So this patch split out the business of lwp_new() to improve the
maintainability.

Signed-off-by: Shell <smokewood@qq.com>

components/lwp/lwp.c

@@ -1152,7 +1152,7 @@ pid_t lwp_execve(char *filename, int debug, int argc, char **argv, char **envp)
         return -EACCES;
     }
 
-    lwp = lwp_new();
+    lwp = lwp_create(LWP_CREATE_FLAG_ALLOC_PID);
 
     if (lwp == RT_NULL)
     {