Adds Copilot Chat Metrics support

[martedesco]

This pull request primarily includes changes to enhance the CopilotChatViewer.vue component and the MetricsData.ts model in the src directory. The most important changes are the addition of new elements and data visualizations to the CopilotChatViewer.vue component, and the extension of the MetricsData.ts model to support new metrics related to chat interactions.

User Interface Enhancements:

• src/components/CopilotChatViewer.vue: Added an API error message to improve user experience when an error occurs.
• src/components/CopilotChatViewer.vue: Introduced two new cards to display the cumulative number of chat turns and lines of code accepted over the last 28 days.
• src/components/CopilotChatViewer.vue: Added charts to visualize the total number of chat acceptances and turns, as well as the total number of active Copilot chat users.
• src/components/CopilotChatViewer.vue: Updated the return statement in the defineComponent function to include new data for the charts and cumulative metrics.
• src/components/CopilotChatViewer.vue: Added new CSS styles for the tiles container.

Data Model Expansion:

• src/model/MetricsData.ts: Expanded the Breakdown and Metrics classes in the data model to include new fields for chat acceptances, chat turns, and active chat users. [1] [2] [3] [4]…