Fix a confusion between 'cleanup' and 'skip_cleanup_if_failed' configuration params

#### Problem
Currently we have configuration params `cleanup` and `skip_cleanup_if_failed`.
Despite their names sound similar, they are responsible for completely different things: `cleanup` controls the database re-creation before each test, and `skip_cleanup_if_failed` controls whether records, added by `haveInDatabase()` should be erased after the test.
#### Suggested fix
It would be good to distinguish these two 'cleanups' in documentation and in the names of config params in next major versions.
For example, to rename `cleanup` to `repopulate` (since we have `populate` responsible for initial database creation).

Issue 提到了設定參數 `cleanup` 和 `skip_cleanup_if_failed`，但沒有指出檔案或測試。首先定位它們的定義和文件，然後確定兩種行為是如何描述的，以及未來的重新命名會影響哪些使用者。完成的標準是明確區分這兩項 cleanup 職責，並針對 major 版本解決所提議的命名變更。

由索引模型根據 Issue 內容生成。