VersionObfuscator bug prevents version reconstruction from String

VersionObfuscator have a bug, preventing
Version reconstruction from String. This PR adds fix + UT

Bug is at line
https://github.com/kazukidb/kazuki/blob/master/kazuki-impl/src/main/java/io/kazuki/v0/internal/helper/VersionObfuscator.java#L100

The line should be changed to
```
return VersionImpl.createInternal(realKey, id);
```

As keyString is actually the password of key encryption.