During the graph Pro feature preview, only count days where the graph was viewed on a private repo

[justinrobots]

1. As a modification to the Pro feature preview Implement a Pro feature preview for the graph #3687 , only count days where the graph was opened on a private repository against the remaining days in the preview. This will give users more time to experience the Pro version of the graph if they are not viewing it every day.

2. As a continuation of the Pro feature modal in the graph Create a confirmation modal for the new graph preview #3689 , add a recurring modal that reminds users how many days are left in a Pro feature preview. This will be displayed each new day after starting the Pro feature preview when a commit graph is opened on a private repository.

Modal content:

• Display a message with the number of days remaining in the Pro feature preview
• Display a message about graph features
• Display 2 CTAs:
  • Continue will dismiss the modal to reveal the graph, and remove a day from the remaining days in the preview.
  • Start 14-day Pro Trial will start the 14 day trial

3. Telemetry when the modal is opened

• how many days are left in the preview
• day preview started
• which CTA is clicked (if any)