Add the total time chart to each VSA stage

What does this MR do and why?

This MR adds the time to completion chart to each stage of the value stream. Additionally some minor improvements are also made to the chart:

• Renames the Days to completion chart to Total time
• Connects each point in the chart with a line (using the median line)
• Moves the chart description into a popover icon next to the chart title
• Minor clean up of the mock data to ensure the duration data is calculated correctly

Screenshots or screen recordings

Overview - no data available	Stage selected - No data available

Recording

• Chart available on all stages
• Updated chart descriptions

Screen_Recording_2022-02-18_at_11.32.32_pm

How to set up and validate locally

Group VSA seeding instructions

1. Ensure you have an EE license, or stub the cycle_analytics_for_groups license feature to true

2. Create a group

3. Create a project within a group (make sure to initialize the project with a readme, or create it from a template)

4. Seed some test VSA data

   $ VSA_SEED_PROJECT_ID=<project-id> VSA_ISSUE_COUNT=10 SEED_VSA=true FILTER=cycle_analytics rake db:seed_fu

Viewing the chart

1. Navigate to value stream analytics for the group, ie for a project named clean-vsa-project in group new-vsa-group it would be http://<gdk>/groups/:group_id/-/analytics/value_stream_analytics (or find it in the left menu)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #346554 (closed)