JOL: Rework magic field offset accessor

There is a report that current trampoline code introduced by CODETOOLS-7902718 causes split packages failures when used on module path:
  https://mail.openjdk.java.net/pipermail/jol-dev/2021-April/000340.html

Additionally, this code does not even work for Record introspection with current JDK 17 EA: the private defineClass is not accessible anymore.

At this point, the only remaining thing left: hack through AccessibleObject overrides. Since this option is dangerous, it should be opt-in, disabled by default.