[14] RFR(M) 8235539: [JVMCI] -XX:+EnableJVMCIProduct breaks -XX:-EnableJVMCI

[Vladimir Kozlov]

https://cr.openjdk.java.net/~kvn/8235539/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8235539

Allow to reset EnableJVMCI and UseJVMCICompiler values on command line when EnableJVMCIProduct flag is used (added by 
JDK-8232118). EnableJVMCIProduct flag sets EnableJVMCI and UseJVMCICompiler to true.

Changes are prepared by Doug for GraalVM and adapted by me for JDK 14.

Passed tier1 where new test runs.

Thanks,
Vladimir