revlog: use context manager for data file lifetime in checksize This is clearer, safer and more modern.

revlog: use context manager for index file lifetime in checkinlinesize This is clearer, safer and more modern.

revlog: use context manager for data file lifetime in checkinlinesize This is clearer, safer and more modern.

revlog: use context manager for index file life time in __init__ This is clearer, safer and more modern.

revlog: move index file opening in a method Having file operation centralized into a single spot help to factor common logic out (eg: special flag handling according to the mode). It is also the first step to simplify file handling during batch operation (eg: revlog cloning). However, that part does not seems to be a hotspot yet.

revlog: move datafile opening in a method Having file operation centralized into a single spot help to factor common logic out. It is also the first step to simplify file handling during batch operation (eg: revlog cloning). However, that part does not seems to be a hotspot yet.

parseindex: implement context manager method on the wrapper This is needed for incoming cleanups.

parseindex: also forward keyword argument in a debug wrapper Otherwise, it gets in the way of a coming refactoring.

dumprevlog: handle being passed a mode parameter This makes it closer to an actual file opener. Otherwise, it gets in the way of a coming refactoring.

changelog: add the missing 'closed' property on 'appender' object This mimic file object further.