Refactoring for better performance of large auto-cli specs

* Fixed: [very slow execution of load_set_file #288](https://github.com/clicon/clixon/issues/288)
* New `clixon-lib@2021-11-11.yang` revision
  * Modified option: RPC stats extended with YANG stats
* Modified `clixon-config@2021-11-11.yang` revision
  * Added option:
    * CLICON_PLUGIN_CALLBACK_CHECK
    * Enable to make plugin context check before and after all callbacks.
* Added statistics for YANG: number of objects and memory used
* Use the treeref no-copy option of CLIgen to reduce memory
* Refactored cli-generation/autocli-start code
* Refactored cligen glue functions to use cligen_eval directly (remove clicon_eval,clixon_cligen_eval)

util/clixon_util_validate.c

@@ -134,6 +134,7 @@ main(int    argc,
 	    break;
 	}
     clicon_debug_init(dbg, NULL);
+    yang_init(h);
     /* Find and read configfile */
     if (clicon_options_main(h) < 0)
 	goto done;