Prolong PR check delay for inactive PRs

[premun]

Context

We are getting rate-limited by GitHub and in order to lower the amount of requests, we can lower the amount of times we check open PRs. Specifically, it seems unnecessary to check all PRs every 5 minutes even when they had no action taken on them for a very long time (even months).
The GitHub API returns a field UpdatedAt or something like that which sounds suitable. We need to read the docs what all this entails.

Goal

Prolong the delay between PR checks for GitHub PRs that have been inactive for very long time.

Something like this:

• Default is 5 minutes
• > week - 15 minutes
• > 2 weeks - 30 minutes
• > 3 weeks - 1 hour
• > month - 12 hours

[dkurepa]

Both GitHub and AzDo APIs have some sort of "last update at" property when fetching a Pull Request, altho they differ:

• On GitHub the updated_at property changes every time there is a change in the PR, this can either a new commit, a comment, a new label, basically anything. This is a good indicator that the PR is being actively worked on.
• On Azdo, there's lastMergeCommit, which isn't really equivalent to this, and tells us just when the last commit in the PR happened, but the times in the API response seem to differ from the times the UI is showing. Since we currently only have a problem with GitHub, we could just proceed as we're used to with AzDo checks

[premun]

Seems like the Scenario Tests are failing since this was merged

[dkurepa]

yeah, something is up with AzDo

[dkurepa]

I fixed issues with AzDo Scenario Tests in the PR above