[nad-viewer] Changing diagram labels

[flo-dup]

Describe the current behavior

Since powsybl-diagram v4.8.0, one may customize completely the style of a network-area diagram thanks to a CustomStyleProvider (see powsybl/powsybl-diagram#670). One may customize it directly with the viewer thanks to setBranchStates / setVoltageLevelStates, but this is limited to

• setBranchStates: the "external" labels (labelB) at each edge extremity
• setVoltageLevelStates: updating the values in the default voltage level legend (angle / voltage)

Describe the expected behavior

Allow to further customize the labels:

• a voltage level legend more specific than the default one
• setting the other labels for the edge infos, especially the middle ones

Describe the motivation

Users want to display very specific informations on edges / buses / voltage levels when studying a network

Extra Information

• for customizing the voltage level legend, see createLegendBox
• for customizing the edge infos at each extremity, see setBranchSideLabel