[Java] unnecessary printStackTrace

Description

In certain conditions, when rendering of a specification fails, Codegen log exception's stack trace to stdout. This happen through an ex.printStackTrace(); in the DefaultGenerator class.
This print is calling directly the stdout stream creating an unnecessary log once this printStackTrace should be catch as an exception and logged properly.

} catch (Exception ex) {
    ex.printStackTrace();
    String msg = "Could not process operation:\n" //
            + "  Tag: " + tag + "\n"//
            + "  Operation: " + operation.getOperationId() + "\n" //
            + "  Resource: " + httpMethod + " " + resourcePath + "\n"//
           // + "  Definitions: " + swagger.getDefinitions() + "\n"  //
            + "  Exception: " + ex.getMessage();
    throw new RuntimeException(msg, ex);
}

The offending line that logs stack trace to stdout is the ex.printStackTrace(); in uk/nhs/digital/apispecs/swagger/CodegenDefaultGenerator.java:144;

This printStackTrace is not present in the 2.X version.

Swagger-codegen version

3.0.25

Steps to reproduce

When rendering of a specification fails due to schemas being referenced rather than embedded, the resulting NullPointerException's stack trace

Suggest a fix/enhancement

Remove the stackTrace line and the user must catch the exception and print it as desire.

Open uk/nhs/digital/apispecs/swagger/CodegenDefaultGenerator.java around line 144 and compare the handling with the 2.X version. Confirm that rendering failures no longer write a stack trace directly to stdout while the existing exception message and cause remain available to the caller.