Add stage container label to update-dependencies-internal pipeline runs

[lbussell]

Working towards #6915.

Adds a label like Container - stage-1234567 to update-dependencies-internal pipeline runs.

AI generated description

This pull request introduces significant improvements to dependency injection, environment abstraction, and Azure Pipelines integration within the eng/update-dependencies tooling. The changes refactor several services to use interfaces and dependency injection, add new abstractions for environment and build labeling, and improve testability and maintainability by removing direct environment variable access. Additionally, new extension methods are introduced for streamlined service registration.

Dependency Injection and Service Abstractions

• Refactored AzdoAuthProvider, AzdoHttpClient, and PipelineArtifactProvider to use interfaces (IAzdoAuthProvider, IPipelineArtifactProvider), enabling easier mocking and testing. Extension methods for registering these services with IServiceCollection were added. [1] [2] [3] [4] [5] [6] [7]
• Introduced IEnvironmentService and its implementation to encapsulate environment variable access, replacing direct Environment.GetEnvironmentVariable calls throughout the codebase. [1] [2]

Azure Pipelines Integration and Build Labeling

• Added IBuildLabelService and its implementation to allow tagging Azure Pipelines builds programmatically, with extension methods for DI registration. [1] [2]
• Updated logic for creating PR branch names to accept a build ID parameter, improving uniqueness and testability. Environment detection and build ID retrieval now use IEnvironmentService. [1] [2] [3] [4] [5]

Code Cleanup and Documentation

• Removed the obsolete AzurePipelinesHelper class, consolidating environment logic into EnvironmentService.
• Updated .github/instructions/csharp.instructions.md to discourage comments like // Arrange, // Act, or // Assert in unit tests.

Service Registration and Composition

• Simplified service registration in Program.cs by using new extension methods for environment, build label, and artifact provider services.

These changes collectively modernize the codebase, improve testability, and make Azure Pipelines integration more robust and maintainable.

[lbussell]

Test run of update-deps-internal-unofficial: build#2884441