This bug manifests due to wrong computation and evaluation of
keyinfo->key_length. The issues were:
* Using table->file->max_key_length() as an absolute value that must not be
  reached for a key, while it represents the maximum number of bytes
  possible for a table key.
* Incorrectly computing the keyinfo->key_length size during
  KEY_PART_INFO creation. The metadata information regarding the key
  such the field length (for strings) was added twice.