Increasing counter cache time

What does this MR do and why?

    Increasing counter cache timeout and fixing nil

   This increases the counter timeout to 2 weeks as some imports can take multiple days to finish.

    Additionally, returns 0 instead of nil when there is no cache. So imports won't be stuck in-progress.

Screenshots or screen recordings

How to set up and validate locally

1. https://docs.gitlab.com/ee/user/project/import/github.html
   1. The realtime importing should still work
   2. After importing, the counts should still be there

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 #421980 (closed)