Add ability to pull the version used to build java from the logstash repo, rather
than rely on system Java. Previously, builds would use JAVA_HOME, now this setting
is ignored in Logstash (and by extension, parts of the Logstash build), which was causing
variations in the version of Java used to build Logstash, including the use of Java 8,
which the Logstash team would like to remove support for.
Relates: https://github.com/elastic/infra/pull/32818
This adds the .ci/matrix-runtime-javas.yml file that defines all
the JDKs logstash could be tested against. This is meant to be
used for the Matrix Combinations Jenkins plugin to be able to
select which JDK to test against dynamically.
To be unlinked from infra and made the selection of OSes that Logstash is tested against, the list is moved .ci specific yaml files.
By now the OSes are distinguished by Windows platform and by Linux distributions.
Separated selection of OSes in CI for compatibility and normal tests
