typing: add type hints to `mercurial.shelve` Pytype wasn't flagging anything here yet, but PyCharm was really unhappy about the usage of `state` objects being passed to various methods that accessed attrs on it, without any obvious attrs on the class because there's no contructor. Filling that out made PyCharm happy, and a few other things needed to be filled in to make that easier, so I made a pass over the whole file and filled in the trivial hints. The other repo, ui, context, matcher, and pats items can be filled in after the context and match modules are typed.