Store TLS opts in lua stack, no strdup/free

Store TLS opts in lua stack, no strdup/free

- Removed g_strdup/g_free of TLS paths in src/lua/lua_redis.c.
- Now we:
  - Keep TLS values (booleans + strings) on the Lua stack temporarily.
  - Use an absolute table index (so gettable calls aren’t confused by
    the growing stack).
  - Call rspamd_redis_pool_connect_ext while those values are on the
    stack.
  - Pop all postponed values and then the table in one go immediately
    after the connect call.
- The C++ pool still copies into std::string on element creation; we
  only ensure Lua strings live through the call without extra
  allocations.