Top Labels for Group Bar Charts no working

### Describe Your Environment

Any RN version and device.

### Describe the Problem

Labels for Grouped Bar charts are not included in the new victory-native-xl library. This feature was in the previous victory library.

**Expected behavior:** To be able to add labels on top of


**Actual behavior:** Labels aren't working in Group Bar Charts. They are only working in single bar charts.

The issue does not name a file or test. Start by locating the grouped-bar label rendering entry point and comparing it with the existing single-bar label behavior. Done means labels render above grouped bar charts on supported React Native devices, with regression coverage for that case.

Written by the indexing model from the issue text.