openjdk: update to 8u232b09, rename to openjdk8, native bootstrap

This updates OpenJDK 8 to a newer version and brings a bunch of
changes.

Newly, it is bootstrapped with openjdk7-bootstrap, so it does not
need to download binaries. It can also cross-compile and is patched
for musl and other platforms.

We're newly using the aarch64 port repo in order to get aarch64
JIT. For non-aarch64 platforms, the codebase is the same.

The symlink for /usr/lib/jvm/openjdk is also now gone and we're
using a unified java-VERSION-VENDOR naming.

Also general template cleanup.

[ci skip]

etc/defaults.virtual

@@ -21,8 +21,8 @@
 
 awk gawk
 emacs emacs
-java-environment openjdk
-java-runtime openjdk-jre
+java-environment openjdk8
+java-runtime openjdk8-jre
 libudev eudev-libudev
 nodejs-runtime nodejs
 ntp-daemon chrony