dirstate: explicitly write the dirstate after `debugrebuilddirstate`

I am working on making the dirstate write patterns more predictable. This patch is
part of a small series of similar patches that adds a explicit dirstate write in
a handful of location where the dirstate is updated "a bit in a strange way".

With this explicit write, we are no longer relying on implicite write of the
dirstate on `wlock` release. This make the world a better place.

mercurial/debugcommands.py

@@ -3140,6 +3140,7 b' def debugrebuilddirstate(ui, repo, rev, '
             changedfiles = manifestonly | dsnotadded
 
         dirstate.rebuild(ctx.node(), ctx.manifest(), changedfiles)
+        dirstate.write(repo.currenttransaction())
 
 
 @command(