scheme: move the drive letter checking in its own function This help the readability of the main function as is was taking much more room than the main logic.

peer-or-repo: split the scheme between repo and peer Some of the scheme will always produce a peer and some will always produce a repository. So lets use different mapping to reduce the ambiguity.

peer-or-repo: stop relying on AttributeError in `islocal` This will confused pytypes in a future changeset.

repo-or-peer: deprecate calling `islocal` on non-path object There object have a `.local()` method and should use it.

share: stop using 'islocal' with repo instance Having this level of polymorphism of the `islocal` function is weird, and we already have a way to know if the repo is local from the object itself. We are about to deprecate passing a non-bytes object to `islocal`, so clean this up beforehand. We might want to clean up this function too in the future, however this is another adventure.

peer-or-repo: make sure object in "scheme" have a `instance` object The previous form of having heterogeneous object in the dictionnary makes things more complicated than they needed to be. I am not super happy about the current (especially around 'islocal', that most item do not have), but this is already much better.

peer-or-repo: move the object setup in its own function The `_peerorrepo` function is problematic, because it can build different types of object (repository and peer). This make it hard to adjust the arguments to the type of object we needs. So this patch start a series of change to create peer and repo without going through a common function. We move the part of the function doing object setup it its own function to make it simpler to reuse in others contexts.