[SPARK-3433][BUILD] Fix for Mima false-positives with @DeveloperAPI and @Experimental annotations.

Actually false positive reported was due to mima generator not picking up the new jars in presence of old jars(theoretically this should not have happened.). So as a workaround, ran them both separately and just append them together.
does this need to be called twice? It's now called here and below as well. If it is needed twice, it would be good to document why,