Use `asHostObject` and simplify handling of `WithWarnings`

[JaroslavTulach]

• the Truffle guys listened to your cries (e.g. HostObject interop with wrapping TruffleObject oracle/graal#4916)
• and implemented [GR-71402] Adding isHostObject and asHostObject interop messages. oracle/graal#12670, thanks @tzezula!
  • the InteropLibrary.asHostObject will be part of Truffle 25.1.0 release once made available
• with that new API available we can modify/simplify our handling of polyglot java interop