journal: use wrapfilecache instead of wrapfunction on func of filecache wrapfilecache() on filecache-ed property works more strictly than wrapfunction() directly on func() of filecache.

journal: execute setup procedures for already instantiated dirstate If dirstate is instantiated before reposetup() of journal extension, it doesn't have "journalstorage" property, even if it is instantiated via wrapdirstate() wrapping repo.dirstate(), because wrapdirstate() works as same as original one before marking repo as "journal"-ing in reposetup(). This issue can be reproduced by running test-journal.t or test-journal-share.t with fsmonitor-run-tests.py. On the other hand, just discarding already instantiated dirstate in reposetup() prevents chg from filling dirstate before reposetup() (see bf3af0eced44 for detail). Therefore, this patch executes setup procedures for already instantiated dirstate explicitly in reposetup(). To centralize setup procedures for dirstate, this patch also factors them out from wrapdirstate().