Java creates an incorrect pipeline proto when core-construction-java jar is not in the CLASSPATH

Seems like Java ends up creating incorrect pipeline API proto segments when "core-construction-java" is not available in the system.

For example, this may create  a GBK transform without the URN. 

This can be reproduced by running the wordcount example in [1] after  removing the following dependency from the pom.xml file.

   
      org.apache.beam
      beam-runners-core-construction-java
      ${beam.version}
   
 
Seems like this is because Java is unable to register corresponding XYZTranslation classes (for example [2]). 
 

I think we should fail here instead of generating default incorrect proto segments.

[1] [https://github.com/chamikaramj/multi-language-pipelines](https://github.com/chamikaramj/multi-language-pipelines)

[2] [https://github.com/apache/beam/blob/master/runners/core-construction-java/src/main/java/org/apache/beam/runners/core/construction/GroupByKeyTranslation.java](https://github.com/apache/beam/blob/master/runners/core-construction-java/src/main/java/org/apache/beam/runners/core/construction/GroupByKeyTranslation.java)

Imported from Jira [BEAM-12807](https://issues.apache.org/jira/browse/BEAM-12807). Original Jira may contain additional context.
Reported by: chamikara.