[foreign] RFR 8221228: JavaSourceBuilderExt.emitStaticForwarder should reuse fillArgTypes and fillArgNames from super class

[Sundararajan Athijegannathan]

Please review.

Bug: https://bugs.openjdk.java.net/browse/JDK-8221228
Webrev: https://cr.openjdk.java.net/~sundar/8221228/webrev.00/

Piggybacking to do few simple test-only fixes as well.

Thanks,
-Sundar