revlog: overwrite revlog config through copy of the config object The new objects allow for this kind of blanket approach that make things cleaner. If we have more cases, it would probably deserve a context manager, but since we only have two usage, I don't think it is worth it.

revlog: move configuration attribute into dedicated object First this make things clearer as the number of configuration attributes has grown out of control, so gathering them make things clearer. Second, this will make future sharing them at different level simpler. Third it will allow us to make initialisation and temporary override simpler soon.

manifestrevlog: flag some inconsistency in bundle/union repo inheritance This "work" but still, this is weird, let us point it out.

randomaccessfile: drop explicit passing of file description The goal of this object is to manage IO, we still have to open the file if necessary, but this is all internal now.