Why do we actually use Unsafe in Scala CLI? Looks like we might need to remove it if possible

Originally posted by @tgodzik in #3920 (comment)

It seems we retain an old hack for lazy vals, which used to be necessary pre-Scala 3.3.
We need to

• check if it's still needed for any reason
  • if yes, make sure it'll handle JDK 24+ well (no warnings)
  • if no, perhaps get rid of it altogether