New Line-Pie Combo Chart

[kedij777]

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior? (You can also link to an open issue here)
Issue #1916

What is the new behavior?
When the mouse is not hovered over the line chart x-axis node, the pie chart displays the sum of the values for each legend group. When the mouse is over one of the x-axis nodes of the line chart, the pie chart shows the distribution of y-values for each country at that x-value.

The combo chart supports all reasonable features of line chart and pie chart respectively.

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

[Lyq322]

Initial pie chart does not change when real-time data is enabled. Only the line chart data changes
Before enabling real-time data:

After enabling: pie chart data does not update

[Lyq322]

Unclear which data is for pie chart and which is for line chart.

[Lyq322]

Fit container does not work. Dimensions were not changed after enabling fit container.
After enabling fit container:

[Lyq322]

Currently, it seems that the two charts are separated by a fixed distance. This causes the pie and line charts to be too far apart when the dimensions are small and too close together when the dimensions are large.

[kedij777]

Unclear which data is for pie chart and which is for line chart.

Thanks for suggestion, fixed.