dev-java/oracle-jdk-bin: Bring 8 ebuild in line with 9 and simplify

dev-java/oracle-jdk-bin: Bring 8 ebuild in line with 9 and simplify

I doubt the MacOS examples were working before.

The pkg_nofetch stuff was needlessly complicated as ${A} already
contains just the relevant files and the function is not called at all
if all files are present.

I noticed that all the demo files follow a pattern, except on MacOS
for some bizarre reason. I doubt any demo files will disappear before
Java 8 is EOL'd but this can easily be handled in the case statement.

Package-Manager: Portage-2.3.19, Repoman-2.3.6