RFR: 8151470: [JVMCI] remove up-call to HotSpotJVMCICompilerConfig.selectCompiler

[Christian Thalinger]

https://bugs.openjdk.java.net/browse/JDK-8151470
http://cr.openjdk.java.net/~twisti/8151470/webrev.01/

The reason why it was done this way is to use a trusted system property value to select the compiler.  We can achieve the same by using VM.getSavedProperty.

This patch changes the system property name from “jvmci.compiler” to “jvmci.Compiler” as it’s using an Option now.

As discussed with Doug I also got rid of some property file parsing code that we don’t need right now.