MDEV-14372: Fix and enable rocksdb.information_schema test

- Make Rdb_binlog_manager::unpack_value to not have a stack overrun
  when it is reading invalid data (which it currently does as we in
  MariaDB do not store binlog coordinates under BINLOG_INFO_INDEX_NUMBER,
  see comments in MDEV-14892 for details).
- We may need to store these coordinates in the future, so instead of
  removing the call of this function, let's make it work properly for
  all possible inputs.

storage/rocksdb/rdb_datadic.h

@@ -46,6 +46,8 @@ class Rdb_field_packing;
 class Rdb_cf_manager;
 class Rdb_ddl_manager;
 
+const uint32_t GTID_BUF_LEN = 60;
+
 /*
   @brief
   Field packing context.
@@ -1154,7 +1156,8 @@ private:
   rocksdb::Slice pack_value(uchar *const buf, const char *const binlog_name,
                             const my_off_t &binlog_pos,
                             const char *const binlog_gtid) const;
-  bool unpack_value(const uchar *const value, char *const binlog_name,
+  bool unpack_value(const uchar *const value, size_t value_size,
+                    char *const binlog_name,
                     my_off_t *const binlog_pos, char *const binlog_gtid) const;
 
   std::atomic<Rdb_tbl_def *> m_slave_gtid_info_tbl;