Tooltips near the edge of the screen should stay on screen

**Describe the bug**

Tooltips appearing near the edge of the screen shouldn't go off screen, they should display to the left of the cursor/touch.

**To Reproduce**

Make a full width bar chart, hover or tap the rightmost bar.

**Screenshots**


**Versions**

```
Flutter 3.27.1
fl_chart: ^0.70.2
```

Start by reproducing the issue with a full-width bar chart and hovering or tapping the rightmost bar. Trace the tooltip positioning used by the bar chart and ensure the tooltip remains on screen by displaying it to the left of the cursor or touch point when needed.

Written by the indexing model from the issue text.