RFR 9: 8064956 : Remove sun.misc.ExtensionInstallationProvider and relevant classes

[Brent Christian]

Hi,

Please review my change for:

Bug:
https://bugs.openjdk.java.net/browse/JDK-8064956
Webrev:
http://cr.openjdk.java.net/~bchristi/8064956/

After clearing some internal dependencies following the removal of the 
extension mechanism from JDK 9[1], we can now remove 4 extension-related 
classes from sun.misc:

ExtensionDependency.java
ExtensionInfo.java
ExtensionInstallationException.java
ExtensionInstallationProvider.java

I will submit a CCC following code review.

Thanks,
-Brent

1. https://bugs.openjdk.java.net/browse/JDK-8061971