fix exception wrapping for Method.invoke and static initializers

Method.invoke should initialize its class before invoking the method,
throwing an ExceptionInInitializerError if it fails, without wrapping
said error in an InvocationTargetException.

Also, we must initialize ExceptionInInitializerError.exception when
throwing instances from the VM, since OpenJDK's
ExceptionInInitializerError.getCause uses the exception field, not the
cause field.