Common interface for tooltip settings #476

We have an idea to create common tooltip settings interface.

Currently, tooltip settings is somehow declared as part of existing widgets:
https://github.com/gravity-ui/chartkit/blob/main/src/plugins/highcharts/types/widget.ts#L52

This means, that we need to prepare these settings according to widget plugin we are using.

It would be better to use common interface, independent on type of widget or plugin we are going to use.

In the meantime we should limit number of places, where tooltip settings can be set.

Currently, we can set tooltip settings in each series and globally for widget for Highcharts:
https://github.com/gravity-ui/chartkit/blob/main/src/plugins/highcharts/types/widget.ts#L52

Places where tooltip settings can be set must be same for each widget type and plugin.