Need to regenerate release history XML files when release nodes are manually published/unpublished

Followup from #184418: update(_status) results stale for up to 6 hours. The one edge case that doesn't yet solve is when release nodes are manually published or unpublished. For example, if the security team publishes a release node once an SA goes out, or if they decide to unpublish releases in response to a vulnerability report or something. In those cases, the Update status results will still be stale for up to 6 hours, unless the sec team manually regenerates the release history files for the affected projects (which is now a lot easier to do thanks to the command-line arg you can pass to project-release-create-history.php to restrict to a single project).

In #184418 there was talk of some kind of dirty bit in {project_release_nodes}, and a mode of invoking project-release-create-history.php that just queries for release nodes with the dirty bit set, regenerates the history, then clears the bit. Not sure what else to do, but if anyone has any bright ideas, I'm all ears.