[14] RFR(S) 8234681: Remove UseJVMCIClassLoader logic from JVMCI code

[Vladimir Kozlov]

https://cr.openjdk.java.net/~kvn/8234681/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8234681

UseJVMCIClassLoader logic is only applicable to graal-jvmci-8. It was ported from graal-jvmci-8 as part of JDK-8220623 
"JVMCI support of libgraal". It is not needed in JDK.

Tested tier1-3

Thanks,
Vladimir