GitHub Labels: Report for new labels created

# Summary

Each of the Azure SDK repositories makes use of a common set of labels for issues and pull-requests. This allows automation rules to be synchronized across repositories and provides a consistent experience for contributors and issue authors. To help keep the common set of labels aligned, this repository contains a set of [tools](https://github.com/Azure/azure-sdk-tools/tree/main/tools/github-labels) aimed at doing so.

To keep the common set of labels up to date, one of these tools inspects the current labels in a repository against a known snapshot, detecting any new labels that were created.
These additions can then be evaluated to determine whether they should be made part of the common set. To optimize this process, it would be desirable to create a report that can perform the task on a schedule and proactively notify team members via email.

# Scope of Work

- The inspection of repository labels and comparison to the known snapshot currently performed by the [`scan-new-labels.ps1`](https://github.com/Azure/azure-sdk-tools/blob/main/tools/github-labels/scan-new-labels.ps1) script should be translated into a report in the [github-issues](https://github.com/Azure/azure-sdk-tools/tree/main/tools/github-issues/Azure.Sdk.Tools.GitHubIssues) area.

- The report should make use of the [set of known snapshots](https://github.com/Azure/azure-sdk-tools/tree/main/tools/github-labels/repository-snapshots) tracked in the `github-labels` area.

- The report should make use of the [set of known repositories](https://github.com/Azure/azure-sdk-tools/blob/main/tools/github-labels/repositories.txt) as the targets to scan.

- This report should be configured to run on a weekly schedule, sending mail to the triage team currently receiving the GitHub Issue reports.

# Success Criteria

- A report exists that detects label changes in GitHub repositories as detailed in the scope.

- The report has been deployed and configured to run on a weekly schedule.

- The report has been tested and produces the same set of data as the [`scan-new-labels.ps1`](https://github.com/Azure/azure-sdk-tools/blob/main/tools/github-labels/scan-new-labels.ps1) script.

# References and Resources

- [Example PR for a new report addition](https://github.com/Azure/azure-sdk-tools/pull/1865)