Please move all `PROXY-*` properties to `ClientProperties`. We may want to re-use it also for other connectors.

Note that I am not asking you to implement the support for them in the other connectors, just to move the properties. You can add a javadoc note that these are now only supported by Jetty connector. Ideally, you can also add a
```
// TODO Need to implement support for PROXY-* properties in other connectors
```
comment before those moved properties.