title: Github action: setup-java with multiple JDKs and corresponding environment variables
body: <p><strong>Background:</strong>
  I've a spring-boot 2.3 project using reactive driver for cassandra that is built on Java 11. For integration test though, when I spin up an embedded Cassandra database, I rely on presence of Java 8 on the machine with accompanying environment variable JAVA8_HOME.</p>
  <p><strong>Question:</strong>
  How can I configure GitHub action <a href="https://github.com/actions/setup-java" rel="nofollow noreferrer">setup-java</a> to utilise multiple JDKs for my build and let JAVA_HOME point to Java 11 but JAVA8_HOME point to Java8?</p>