ci : use selective copy for musa image (#3296)

This commit modified the musa docker file to selectively copy
directories needed for the container image.
This commit also added a step to the docker workflow to free up disk
space in attempt to make enough room for the large musa build
containers.

The motivation for this change is to reduce the size of the container
image and try to avoid disk usage issues in CI.

.devops/main-musa.Dockerfile

@@ -32,8 +32,9 @@ RUN apt-get update && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/* /var/cache/apt/archives/* /tmp/* /var/tmp/*
 
-COPY --from=build /app /app
-RUN du -sh /app/*
-RUN find /app -type f -size +100M
+COPY --from=build /app/build/bin /app/build/bin
+COPY --from=build /app/samples /app/samples
+COPY --from=build /app/models /app/models
+
 ENV PATH=/app/build/bin:$PATH
 ENTRYPOINT [ "bash", "-c" ]