Redis [BUG][FUNCTION]load exists libraries cause libraries_count increase

Describe the bug load exists libraries will return ERR， bug the metric libraries_count & functions_count will increase

To reproduce

27.0.0.1:6379> FUNCTION stats
1) "running_script"
2) (nil)
3) "engines"
4) 1) "LUA"
   2) 1) "libraries_count"
      2) (integer) 1
      3) "functions_count"
      4) (integer) 1
127.0.0.1:6379> FUNCTION LOAD "#!lua name=mylib\nredis.register_function('knockknock', function() return 'Who\\'s there?' end)"
(error) ERR Library 'mylib' already exists
127.0.0.1:6379> FUNCTION stats
1) "running_script"
2) (nil)
3) "engines"
4) 1) "LUA"
   2) 1) "libraries_count"
      2) (integer) 2
      3) "functions_count"
      4) (integer) 2
127.0.0.1:6379>

Expected behavior https://github.com/redis/redis/blob/unstable/src/functions.c#L966 goto error and relink library， so in libraryLink increase stats->n_lib and stats->n_functions。

Comment From: enjoy-binbin

verified. i take a quick look, random thoughts: 1. dictAdd(lib_ctx->libraries, li->name, li); look like we need to check the return value 2. look like we need a flag like old_li_already_exists, when the lib already exists, set to 1, and libraryLink(lib_ctx, old_li) only if old_li_already_exists == 0

Comment From: MeirShpilraien

Thanks @enjoy-binbin, please let me know what you think about this fix: https://github.com/redis/redis/pull/10706