Show ansi colors in azdo and gh actions CI

[nohwnd]

Port of this for new dotnet test experience with MTP microsoft/testfx#5535

Related to #45927

[Copilot]

Pull Request Overview

Adds CI-friendly ANSI rendering and dark color variants for test output in Azure DevOps and GitHub Actions.

• Introduce UseCIAnsi flag and simple CI detection to select a CI-compatible ANSI terminal.
• Implement SimpleTerminalBase and SimpleAnsiTerminal for streamlined ANSI output in CI.
• Change default terminal colors to darker variants and refactor NonAnsiTerminal to remove duplication.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Cli/dotnet/Commands/Test/TestingPlatformCommand.cs	Add CI detection and pass UseCIAnsi into reporter options
src/Cli/dotnet/Commands/Test/Terminal/TerminalTestReporterOptions.cs	Define new UseCIAnsi property
src/Cli/dotnet/Commands/Test/Terminal/TerminalTestReporter.cs	Switch to SimpleAnsiTerminal in CI and update default colors
src/Cli/dotnet/Commands/Test/Terminal/SimpleTerminalBase.cs	New base class consolidating terminal behaviors
src/Cli/dotnet/Commands/Test/Terminal/SimpleAnsiTerminal.cs	Implement simplified ANSI terminal for CI
src/Cli/dotnet/Commands/Test/Terminal/NonAnsiTerminal.cs	Refactor to inherit from SimpleTerminal and remove custom batching/progress logic
src/Cli/dotnet/Commands/Test/Terminal/AnsiTerminalTestProgressFrame.cs	Update progress frame colors to dark variants

Comments suppressed due to low confidence (3)

src/Cli/dotnet/Commands/Test/TestingPlatformCommand.cs:143

• CI ANSI output is enabled even when the user requests no ANSI (--no-ansi) because UseCIAnsi is checked without verifying UseAnsi. Change this to if (_options.UseAnsi && _options.UseCIAnsi) so that CI ANSI mode respects the --no-ansi flag.

if (_options.UseCIAnsi)

src/Cli/dotnet/Commands/Test/TestingPlatformCommand.cs:131

• No tests cover the new CI environment detection or the UseCIAnsi flag. Consider adding unit tests that set TF_BUILD and GITHUB_ACTIONS environment variables to validate that inCI and UseCIAnsi behave as expected.

// TODO: Replace this with proper CI detection that we already have in telemetry. https://github.com/microsoft/testfx/issues/5533#issuecomment-2838893327

src/Cli/dotnet/Commands/Test/Terminal/SimpleTerminalBase.cs:56

• The new RenderProgress implementation in SimpleTerminalBase dropped the /r indicator for retried failed tests that existed in the original NonAnsiTerminal. This regression means retried counts won’t be shown. Restore the retried-test logic or extend RenderProgress to include p.RetriedFailedTests when > 0.

public void RenderProgress(TestProgressState?[] progress)