RFR [9] 8146774: Remove sun.misc.JarFilter

[Chris Hegarty]

JarFilter was used solely by implementation of the extension mechanism,
which itself was removed by 8064956 [1]. JarFilter should probably have
been removed along with the other extension implementation, it was
probably just overlooked. It should be removed.

$ hg rm src/java.base/share/classes/sun/misc/JarFilter.java

-Chris.

[1] https://bugs.openjdk.java.net/browse/JDK-8064956