Finish onboarding Rust to common pipelines

https://github.com/Azure/azure-sdk-tools
- [x] eng\common\pipelines\templates\jobs\prepare-pipelines.yml
- [x] eng\pipelines\agent-pool-migration.yml
- [x] eng\pipelines\branch-cleanup.yml (partial)
- [x] eng\pipelines\eng-common-sync.yml
- [x] eng\pipelines\eng-workflows-sync.yml
- [x] eng\pipelines\git-tasks.yml
- [x] eng\pipelines\mirror-repos.yml
- [x] eng\pipelines\pipeline-generation.yml
- [x] eng\pipelines\tools-repo-versioning.yml
- [x] eng\pipelines\templates\jobs\stress-test-release.yml
- [x] eng\scripts\Approve-Eng-Common-Sync-PRs.ps1
- [x] eng\scripts\Create-Package-WorkItem.ps1
- [x] eng\scripts\github-statistics.ps1
- [x] tools\github\data\repositories.txt
- [x] tools\issue-labeler\src\Azure.Sdk.Labels\AzureSdkCombinedLabelModelTrainer.cs
- [x] tools\perf-automation\tests.yml
- [x] tools\pipeline-witness\monitored-repos.json
- [x] tools\test-proxy\Azure.Sdk.Tools.TestProxy\README.md

https://github.com/Azure/azure-sdk
- [x] README.md