RFR: 8249149 Remove obsolete UseNewFieldLayout option and associated code

[Frederic Parain]

Please review this patch removing the old field layout code
that was deprecated in JDK15.

CR: https://bugs.openjdk.java.net/browse/JDK-8249149

Webrev: http://cr.openjdk.java.net/~fparain/8249149/webrev.00/index.html

Tested with tier 1 to 3.

Thank you,

Fred