`BarChartRodData.borderRadius` does not support `BorderRadiusDirectional`

**Describe the bug**
`BarChartRodData.borderRadius` does not support `BorderRadiusDirectional`, as its type is constrained to the `BorderRadius` implementation instead of the abstract `BorderRadiusGeometry` representation.

The same happens with `FlBorderData.border`, which expects a `Border` instead of a `BorderGeometry`.

It may be a feature rather than a bug, but I vote for the ability to use these directionality utilities.

**To Reproduce**
Provide a `BorderRadiusDirectional` object into the `BarChartRodData.borderRadius` property, or into `FlBorderData.border`.

**Screenshots**

**Versions**
- which version of Flutter are you using? **3.3.9**
- which version of FlChart are you using? **0.55.2**

Start by locating the definitions and usages of BarChartRodData.borderRadius and FlBorderData.border. Check how their current types are used across the chart widgets, then verify that BorderRadiusDirectional and BorderGeometry values can be passed through both entry points without breaking existing behavior.

Written by the indexing model from the issue text.