sidedata: gate sidedata functionality to revlogv2 in more places Since revlogv1 is not capable of storing sidedata, we prevent sidedata mechanisms around the revlog layer from doing anything. We however keep the ones that allow a revlogv1 repo to generate sidedata on-the-fly on a push, the pull case simply does not add the sidedata to the revlog. Differential Revision: https://phab.mercurial-scm.org/D10341