Direct Runner cannot be run on non Java LTS versions

Users of Direct Runner on non LTS Java versions e.g. Java 9, 10, 12, 13, ... cannot run Beam pipelines on Java's Direct runner because It fails with "UnsupportedOperationException unsupported Java version: X".

This is probably a requirement for the portability case because there won't be available a SDK Harness for non LTS versions of Java, however it is a too strict requirement for Direct Runner where users provide the Java environment locally.

https://github.com/apache/beam/blob/3f1432d1c23790a1522d90ba3c2f2ed787eee383/runners/core-construction-java/src/main/java/org/apache/beam/runners/core/construction/Environments.java#L121