Fix usage of callable_deprecation on LazyObject that was breaking CW 3.24 (or something like that)

So, brace yourself, it's a little bit complicated (don't hesitate to reach me for more explanation).

So, it goes like that:

• I've introduced the usage of the @wraps decorator from functools.wraps in logilab.common.deprecation.callable_deprecated because this is a good practice
• turns out if broke francearchives code
• which is because it uses an old version of CW
• in this old version of CW, logilab.common.modutils.LazyObject is used (well, inherited) here https://forge.extranet.logilab.fr/cubicweb/cubicweb/blob/3.24.0/cubicweb/schemas/__init__.py#L51
• LazyObject all you to do something like exists = LazyObject("os.path", "exists") and up until exists is used, the import is not triggered
• here "used" means "access attributes or call it"
• so, CW uses (My)LazyObject to prepare to import a bunch of cubes (but not importing them) and mark them as callable_deprecated
• this allow to raise a deprecation warning if they are used but not add those cubes as dependencies in CW

Now, why is it a problem? Well ...

• turns out: functools.@wraps actually try to access a bunch of attributes on the wrapped callable to grab __name__, 'dict, '__doc__ to avoid breaking a bunch of stuff
• going back to before, you might have guessed it: by trying to access those attributes, functools.@wraps triggers the import of those objects
• which in turns breaks everything because this is supposed to be a lazy import and so it was supposed to handle the case where those dependencies weren't installed
• and you get an ImportError and your code doesn't work anymore

So, this MR:

• recreate the behavior of functools.wraps but in a lazy way to solve this issue
• it also ensure that we never access attributes of the decorated callable before this decorated callable is actually called
• document LazyObject because pffff

I think it's the first time I had to debug one exception that triggered 3-4 other exceptions ^^'

Also protip: uses pdbpp instead of pdb, it allows to access hidden frames.

added to review label

mentioned in merge request !17 (merged)

merged