[PR Workflow] Automatic ARM sign-off for TypeSpec-based PRs

We have now reached a state with the set of linter rule automation that have been put in place where we can start enabling more self-serve scenarios and simplify the PR review process for RP owners.

The first step towards this is to automatically sign-off the PRs that are raised for open api specs that are generated from Typespec. After reviewing a bunch of PRs that were created for Typespec based PRs, we have reached a conclusion that we can automatically sign-off these PRs without requiring a manual review.

Criteria to be met for an automatic sign-off
- No errors reported by the swagger linter rules (`Swagger Lintdiff` and `Swagger Lintdiff (RPaaS)`)
- Open API spec is generated from TypeSpec
- note by @konrad-jamrozik: this depends on #7353

Mechanism to indicate sign-off
- Add a new label when the above criteria is met, label name suggestion - "ARMAutomaticSignOff".
- The automated merging criteria needs to take this label into account. The existence of one of ARMSignedOff or ARMAutomaticSignOff labels will be used as a way to determine whether the PR was signed off by ARM.

Prerequisites before this automation is put in place in production
- One final linter rule update to production by end of November that has some important fixes

Edit by kojamroz:

Related doc in ARM wiki:
- [Pull Request 9459836](https://msazure.visualstudio.com/One/_git/AzureUX-ARMWiki/pullrequest/9459836): API review best practice and self attestation checklist for Typespec based PRs