[repository] move cnxset pool handling to a helper class
The class has responsability to handle connections pool operations in a single
public attribute 'cnxsets'.
On Repository _get_cnxset() and _free_cnxset() are replaced by cnxsets.get()
and cnxsets.release().
Drop multiple access to private attributes and methods from outside of Repository.
[MASTER]
load-plugins=cubicweb.pylintext
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[MESSAGES CONTROL]
disable = too-many-ancestors,too-many-instance-attributes,too-many-public-methods,
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[BASIC]
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[TYPECHECK]
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[CLASSES]
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# namedtuple public API.
_asdict,_fields,_replace,_source,_make
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