RFR 8216470: Some methods of System.Logger are unimplemented in PlatformLogger

[Arunprasad Rajkumar]

Hi Kevin, Ajit,

Please review the following PR which fixes JDK-8216470.

https://github.com/javafxports/openjdk-jfx/pull/343/

https://bugs.openjdk.java.net/browse/JDK-8216470

Thanks,
Arun