cubicweb #4487856 Preference page "open all" is slow due to high number of AJAX calls [validation pending]

Each time a preference section is opened or closed, dozens of AJAX calls are made to the "i18n" ajax controller to fetch 2 translated strings.

prioritynormal
typeenhancement
done in3.19.6
load0.500
load left0.000
closed by#326fbc5c92b0 [web] Cache results from 'i18n' ajax controller (closes #4487856)
patch[web] Cache results from 'i18n' ajax controller (closes #4487856) [applied]