See https://github.com/jboss-container-images/openjdk/issues/494

Downstream images want a way of appending JVM arguments without overriding the ones we provide and ideally without blocking the user doing the same via JAVA_OPTS_APPEND

Proposed solution: rework the run script to source all scripts under a given path and use the output of each of those to extend the list of JVM arguments. We can move logging, proxy, possbily GC etc. options to use this scheme, and downstream images need only drop a script in the directory to extend it.

PoC: https://github.com/jboss-container-images/openjdk/compare/ubi9...jmtd:gh-494-jvm-args#diff-e38c49939e67e17236485b64a7afc257e6b78a92f42e9654aac965f225fb00a4