ENG-4568: Add utility method to wrap a collection of listenable futures into one.
ENG-4568: Add utility method to wrap a collection of listenable futures into
one.

migue/voltdb,deerwalk/voltdb,paulmartel/voltdb,flybird119/voltdb,kumarrus/voltdb,kumarrus/voltdb,wolffcm/voltdb,paulmartel/voltdb,creative-quant/voltdb,kumarrus/voltdb,zuowang/voltdb,paulmartel/voltdb,simonzhangsm/voltdb,wolffcm/voltdb,flybird119/voltdb,simonzhangsm/voltdb,simonzhangsm/voltdb,zuowang/voltdb,wolffcm/voltdb,ingted/voltdb,VoltDB/voltdb,paulmartel/voltdb,flybird119/voltdb,flybird119/voltdb,ingted/voltdb,wolffcm/voltdb,migue/voltdb,migue/voltdb,simonzhangsm/voltdb,simonzhangsm/voltdb,migue/voltdb,simonzhangsm/voltdb,zuowang/voltdb,flybird119/voltdb,migue/voltdb,paulmartel/voltdb,VoltDB/voltdb,ingted/voltdb,zuowang/voltdb,VoltDB/voltdb,deerwalk/voltdb,wolffcm/voltdb,kumarrus/voltdb,ingted/voltdb,deerwalk/voltdb,zuowang/voltdb,wolffcm/voltdb,paulmartel/voltdb,wolffcm/voltdb,simonzhangsm/voltdb,ingted/voltdb,simonzhangsm/voltdb,creative-quant/voltdb,creative-quant/voltdb,creative-quant/voltdb,ingted/voltdb,kumarrus/voltdb,kumarrus/voltdb,deerwalk/voltdb,deerwalk/voltdb,creative-quant/voltdb,deerwalk/voltdb,kumarrus/voltdb,zuowang/voltdb,deerwalk/voltdb,creative-quant/voltdb,ingted/voltdb,flybird119/voltdb,creative-quant/voltdb,VoltDB/voltdb,flybird119/voltdb,paulmartel/voltdb,VoltDB/voltdb,wolffcm/voltdb,flybird119/voltdb,paulmartel/voltdb,VoltDB/voltdb,migue/voltdb,zuowang/voltdb,creative-quant/voltdb,VoltDB/voltdb,migue/voltdb,zuowang/voltdb,migue/voltdb,kumarrus/voltdb,ingted/voltdb,deerwalk/voltdb