Custom tooltip handler

When the configuration options cannot meet the display requirements of the tooltip, we also provide the ability to customize the tooltip.

Note:

• When a custom tooltip handler is set for the chart, the built-in tooltip will no longer work.
• VChart does not perceive and manage the rendering of custom tooltips. Please implement the tooltip rendering according to your needs, including processing raw data, tooltip content design, and creating components and setting styles according to the project environment.
• When the chart is deleted, the release function of the current tooltip handler will be called, please delete it as needed.
• Since the custom tooltip handler will override the built-in tooltip logic, some tooltip configuration items in the chart spec will no longer work.