Add GitHub AppID and key authentication to commenter bot

[tnozicka]

What would you like to be added:
I'd like to extend the commenter robot flags, so it can be used with GitHub AppID credentials.

(I understand that GitHub apps can authenticate only for a single installation ID, so the queries will be limited to single org, if such authentication option is used.)

Why is this needed:
The commenter robot accepts only GH token for authentication. This is problematic because it needs a real GH user which will incur additional cost for organizations. More importantly, I have tried creating such account and generating long-lived access token for it in "Developer options" but even with --ceiling=10 and the job run every hour, it got flagged by GitHub after the first run(s) which made its comments invisible to anyone else. My hope it using the GitHub App avoids these bans and is similar to native GitHub workflows that get the automatic token.

/assign

[tnozicka]

/sig testing

[k8s-triage-robot]

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/lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle rotten
• Close this issue with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle rotten

[tnozicka]

/remove-lifecycle rotten
/triage accepted
(I'll try to get back to the PR soon)