Vector API's ergonomics is incorrect

* Reproduce
```
java \
  --add-modules=jdk.incubator.vector \
  -XX:+UnlockExperimentalVMOptions \
  -XX:+EnableVectorReboxing \
  -Xlog:compilation \
  -version
```

* The output will be:
```
OpenJDK 64-Bit Server VM warning: Disabling EnableVectorReboxing since EnableVectorSupport is turned off.
[0.222s][info][compilation] EnableVectorSupport=true
[0.222s][info][compilation] EnableVectorReboxing=false
[0.223s][info][compilation] EnableVectorAggressiveReboxing=false
```

So EnableVectorReboxing is actually set fasle, which is unexpected.
It's also incorrect for EnableVectorAggressiveReboxing.