[IMP] chart: allow multiples labels

[anhe-odoo]

Task Description

This PR aims to allow the usage of multiple ranges for a chart labels. This is a necessary step to have a full compatibility to the new treemap chart when switch from chart type, as well as a good way to "categorize" the labels with, for example, the first label ranges being the main category ("Art", "Sciences", ...) and the second label being the real label ("Math", "Chemistry", "Drawing", "Theatre", ...).

Related Task

• Task: 4460827

[robodoo]