revlog: fix _cache usage in revision() As documented at revlog.__init__, revlog._cache stores raw text. The current read and write usage of "_cache" in revlog.revision lacks of raw=True check. This patch fixes that by adding check about raw, and storing rawtext explicitly in _cache. Note: it may slow down cache hit code path when raw=False and flags=0. That performance issue will be fixed in a later patch. test-revlog-raw now points us to a new problem.