[VisBuilder] Add Pie Chart visualization type

[ashwin-pc]

Users should be able to create pie charts in VisBuilder.

Requirements:

• Using the Vis Builder instructions, add Pie chart as a new visualization type
• May either implement using existing VisLib pie chart vis type and expression or using vega-lite (after completion of [VizBuilder] Integrate with vega-lite-expression  #2378)
• Not necessary to migrate all existing options from the existing Pie chart, just identify the minimum reasonable options to implement in Vis Builder.
• Manually validate by creating pie charts with traditional visualization tool and Vis Builder
• Update tests in functional test repo

[vagimeli]

opensearch-project/documentation-website#2279

[ashwin-pc]

@vagimeli This is an issue for the Pie chart implementation in VisBuilder, and not the existing visualization.

[joshuarrrr]

Bumping to 2.6.0 release target.,