clfilter: ensure changegroup generation is run unfiltered Changegroup generation logic needs to be aware of the whole repository to work properly.

clfilter: ensure `rollback` is run unfiltered Rollback logic needs to be aware of the whole repository to work properly.

clfilter: ensure cache invalidation is done on the main unfiltered repo The proxy version will not hold any cache for now. But we have to ensure all cache operations are done on the unfiltered version.

clfilter: ensure that tag logic runs unfiltered The current tag logic is not aware of filtering. We keep the status quo, ensuring that the tag cache is computed as before: without any filtering.

clfilter: ensure `branchcache` logic runs unfiltered The current branchcache construction is not aware of filtering. We keep the status quo, ensuring that the branch cache logic is computed as before: without any filtering.

clfilter: introduce an `unfilteredmethod` decorator This decorator ensure the method in run on an unfiltered version of the repository. See follow-up commit for details. This decorator is not named `unfiltered` because it would clash with the `unfilteredmethod` on `localrepo` itself.