Exclude issues/prs from area pods for arch- and os- labels

[jeffhandley]

Fixes #55

This introduces the concept of exclusion labels and it sets the exclusion labels per repo, with the dotnet/runtime repo's exclusion labels being those with arch- and os- labels that have assigned leads/owners.

1. New rules are added for when an Issue or Pull Request is Excluded
   • When an issue or PR is updated
   • If it's on the area pod's project board
   • And it has one of the exclusion labels
   • The issue is removed from the project board
2. The existing Issue Needs Triage and Pull Request Needs Champion rules are updated
   • When the issue or PR is otherwise destined for the area pod's project board
   • But it has one of the exclusion labels
   • It will not be added to the board

This PR includes recognition of a test-exclusion Used for testing the area pod exclusion rules label within this repository so that we can test this logic from this repo once merged here.

Note for @tarekgh -- I was previously confident that we had concluded not to remove cards from the project board when the issue was moved to a different area; I was wrong. We do remove the cards from the old boards in those cases. I followed suit here, and we will remove cards from area pod boards if they gain one of the arch- or os- labels.

[eiriktsarpalis]

Many benchmark regression issues come with an arch label (sometimes mistakenly so as the regression is not always arch specific), so I think it's important for area owners to have some visibility on these. Perhaps we could limit exclusion to triaged issues only?

[tarekgh]

Many benchmark regression issues come with an arch label (sometimes mistakenly so as the regression is not always arch specific), so I think it's important for area owners to have some visibility on these. Perhaps we could limit exclusion to triaged issues only?

I think we are excluding only arch-wasm. so, this should work fine with the perf issues.

"runtime": [
    "os-android",     // @steveisok; @akoeplinger
    "os-maccatalyst", // @steveisok
    "os-ios",         // @steveisok; @vargaz
    "os-tizen",       // @alpencolt; @gbalykov, @hjleee, @wscho77, @clamp03
    "os-tvos",        // @steveisok; @vargaz
    "arch-wasm",      // @lewing; @BrzVlad
  ],

[jeffhandley]

Good call-out, @eiriktsarpalis. For the os- and arch-wasm labels, we do have folks assigned to monitor them as @tarekgh mentioned. But we'll need to make sure we only use these exclusions for labels where the alternate responsibility is clear.