manifest: add unionmanifestlog support As part of deprecating manifest, we need to make the union repo support manifestlog.

manifest: add bundlemanifestlog support As part of deprecating manifest.manifest we need to make bundlerepo support manifestlog.

manifest: make manifestlog use it's own cache As we start to make manifestlog the primary manifest source, the dependency on manifest.manifest will cause circular dependency problems. Let's break this dependency by making manifestlog use it's own cache. In a near future patch we will remove the previous manifest cache so we're not duplicating it.