cubicweb-elasticsearch #17079905 make a single consistent entry point to compute indexable attributes [validation pending]

For now, index-in-es and standard hooks don't use the same attribute list.

priorityimportant
typeenhancement
done in0.6.0
load0.500
load left0.000
closed by#4cb5b3c2a4b3 [IFullTextIndexSerializable] use fulltext_indexable_attributes attribute to update cw_attr_cache
patch[IFullTextIndexSerializable] use fulltext_indexable_attributes attribute to update cw_attr_cache [applied]