Convert packaging upgrade tests to java (#60560)

This commit removes the last of the bats tests, converting the rpm/deb
upgrade tests to java. It adds a new pattern of tasks, similar in nature
but separate from the existing distro tests, named `distroUpgradeTest`.
For each index compatible version, a `distroUpgradeTest.VERSION` task
exxists. Each distribution then has a task, named
`distroUpgradeTest.VERSION.DISTRO`.

One thing to note is these new tests do not cover no-jdk versions of
the rpm/deb packages, since the distribution/bwc project does not
currently build those.

closes #59145
closes #46005

buildSrc/src/main/java/org/elasticsearch/gradle/ElasticsearchDistribution.java

@@ -244,11 +244,6 @@ public Iterator<File> iterator() {
         return configuration.iterator();
     }
 
-    // TODO: remove this when distro tests are per distribution
-    public Configuration getConfiguration() {
-        return configuration;
-    }
-
     // internal, make this distribution's configuration unmodifiable
     void finalizeValues() {