We should use Options::useOSLog to trigger initializeDatafileToUseOSLog

[Yijia Huang]

The current implementation to initializeDatafileToUseOSLog is based on useOSLogOptionHasChanged, which is inconvenient for some cases due to useOSLogOptionHasChanged can only be updated in std::optional<OptionsStorage::OSLogType> parse(const char* string) with condition `result && result.value() != Options::useOSLog()`.

```
    if (useOSLogOptionHasChanged) {
        initializeDatafileToUseOSLog();
        useOSLogOptionHasChanged = false;
    }
```

```
    if (result && result.value() != Options::useOSLog()) {
        useOSLogOptionHasChanged = true;
    }
```

That means we only can trigger initializeDatafileToUseOSLog() by passing an environment variable other than useOSLog::None. So, the following cases would fail to trigger the initialization function:
case 1: change OSLogType::None to OSLogType::Error in OptionsList.h and pass an environment variable `useOSLog=1`
case 2: only change OSLogType::None to OSLogType::Error in OptionsList.h

We can resolve this by using this
```
    if (Options::useOSLog() != OSLogType::None)
        initializeDatafileToUseOSLog();
```

[Radar WebKit Bug Importer]

<rdar://problem/99500809>