[rset] Always complete attribute/relation caches in ResultSet.get_entity RQL queries are often designed to fill up the ORM's caches when fetching entities out of the result set. Until now, if an entry already existed in the entity cache, ResultSet.get_entity would return it unchanged, not using the new ResultSet's contents to update the attribute cache, breaking expectations (if the attributes are needed, they'd then be fetched later one at a time, one entity at a time), resulting in loads of DB accesses. So we change ResultSet.get_entity so that: * if the entity is already cached and has been instantiated from the same rset, it is returned as-is (to avoid loops) * if the entity is not yet cached, it is instantiated * if the entity is cached via another rset, its attribute/relation caches are completed Closes #9942503

CSS Coding Standards
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(Draft, to be continued)

:Naming: camelCase

Indentation rules
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- 2 espaces avant les propriétés

- pas d'espace avant les ":", un espace après

- 1 seul espace entre les différentes valeurs pour une même propriété


Documentation
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Please keep rules semantically linked grouped together, with a comment about
what they are for.

Recommendation
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- Try to use existing classes rather than introduce new ones

- Keep things as simple as possible while in the framework

- Think about later customization by application

- Avoid introducing a new CSS file for a few lines of CSS, at least while the
  framework doesn't include packing functionalities