Incorrect display format for horizontal bar charts when using formatter functions

[fabio-sp]

Description

When displaying an horizontal bar chart, x axis format is not correctly shown on the tooltip. The values displayed on the axis itself are correctly formatted using the x-axis formatter function, but the values shown in the tooltip are formatted using the y-axis formatter (if provided).

I'm willing to triage this issue but since I'm not familiar with the codebase some guidance could be helpful.

Steps to Reproduce

1. Create a chart with chart type 'bar' and plotOptions.bar.horizontal 'true';
2. Apply a fomatter function on both axes;
3. Render the chart;

Expected Behavior

Actual Behavior

Screenshots

Reproduction Link

https://codepen.io/FabioSpa/pen/QWRjvMY