clfilter: add a propertycache that must be unfiltered Some of the localrepo property caches must be computed unfiltered and stored globally. Some others must see the filtered version and store data relative to the current filtering. This changeset introduces two classes `unfilteredpropertycache` and `filteredpropertycache` for this purpose. A new function `hasunfilteredcache` is introduced for unambiguous checking for cached values on unfiltered repos. A few tweaks are made to the property cache class to allow overriding the way the computed value is stored on the object. Some logic relative to _tagcaches is cleaned up in the process.