RFR: 8160730: [JVMCI] compiler selection should work without -Djvmci.Compiler

[Doug Simon]

Currently, JVMCI compiler selection requires setting the jvmci.Compiler system property. This webrev removes the requirement for explicitly setting the jvmci.Compiler system property if there is only one compiler factory available or if the set of available compiler factories has an inherent selection preference total ordering. It also revives 
JvmciNotifyInstallEventTest and modifies it to test that auto-selection of a JVMCI compiler works in the case where there’s exactly one compiler factory available.


https://bugs.openjdk.java.net/browse/JDK-8160730
http://cr.openjdk.java.net/~dnsimon/8160730/

-Doug