manifest: move dirlog up to manifestrevlog This removes dirlog and its associated cache from manifest and puts it in manifestrevlog. The notion of there being sub-logs is specific to the revlog implementation, and therefore belongs on the revlog class. This patch will enable future patches to move the serialization logic for manifests onto manifestrevlog, which will allow us to move manifest.add onto manifestlog in a way that it just calls out to manifestrevlog for the serialization.

manifest: move revlog specific options from manifest to manifestrevlog The manifestv2 and treeondisk options are specific to how we serialize the manifest into revlogs, so let's move them onto the manifestrevlog class. This will allow us to add a manifestlog.add() function in a future diff that will rely on manifestrevlog to make decisions about how to serialize the given manifest to disk. We have to move a little bit of extra logic about the 'dir' as well, since it is used in conjunction with the treeondisk option to decide the revlog file name. It's probably good to move this down to the manifestrevlog class anyway, since it's specific to the revlog.