Move more clinit code to registration functions

Part 2, attempt 2. Moving the java.net packages
clinit code in previous attempt caused failure
in art test 119-noimage-patchoat. I'm yet to
figure out the root cause of the failure.

Moved clinit code that fetches field/method ids
to JNI registration funcitons. This will allow to
compile-time initialize these classes.

Removed sun.nio.ch.Util#load() method that
was preventing many sun.nio.ch.* classes from
being compile-time initialized.

Bug: 28153851
Change-Id: I5443e5a60a3bf0420fdfec5b91155cef611f8c3d