RFR: 8232118 - Add JVM option to enable JVMCI compilers in product mode

[Bob Vandette]

Please review this RFE that adds a new JVM option "-XX:+EnableJVMCIProduct" which will allow JVMCI to be used as the default compiler, 
and alter a collection of JVM options to be product flags rather than experimental flags. 

EnableJVMCIProduct is an experimental flag since the default JVMCI running mode is still experimental. A vendor wishing to support their JVMCI compiler as the default can enable JVMCI by default by specifying this new -XX:+EnableJVMCIProduct flag after the -XX:+UnlockExperimentalVMOptions flag. This flag is especially useful when added to a JDK runtime generated with the new jlink --add-options plugin (see JDK-8232080 [1]). This allows JVMCI based compilers to be used, by default, without the user having to specify any options. 

RFE:         https://bugs.openjdk.java.net/browse/JDK-8232118
WEBREV: http://cr.openjdk.java.net/~bobv/8232118/webrev.01

[1] Related RFE: https://bugs.openjdk.java.net/browse/JDK-8232080

Bob.