Move more clinit code to registration functions

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

Moved more classes in java.net.* and java.io.*
packages.

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

More clinit code moving changes will follow.

Bug: 28153851
Change-Id: I661bea4d04470366ea589a9308cb2767000c687c