Simplify TerminalOutputDevice

[Youssef1313]

The _firstCallTo_OnSessionStartingAsync field is not very trivial to understand at a first glance. So refactoring this out. How it used to work is:

• It defaults to true.
• It's set to false in OnTestSessionStartingAsync (this called ONLY in the testhost).
• End result is
  • in testhost: the value of this field is false
  • in testhost controller: the value of this field is true.
  • So the variable is semantically "is out of process"

Now that we have already HandleProcessRole, I'm using that to directly store the role of the current process.

This also means we no longer need any logic in OnTestSessionStartingAsync and we don't need to implement ITestSessionLifetimeHandler.

[Copilot]

Pull request overview

This PR updates the platform’s terminal output device to rely on the test process role (TestHost/Controller/Orchestrator) rather than ITestSessionLifetimeHandler callbacks for certain behaviors, and updates the Playground sample to always enable TRX reporting.

Changes:

• Remove ITestSessionLifetimeHandler implementation from TerminalOutputDevice and switch logic to use TestProcessRole.
• Track process role via HandleProcessRoleAsync and use it to decide when to complete the run and how to classify artifacts as out-of-process.
• Enable TRX reporting by default in the Playground sample and add the required project reference.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/Platform/Microsoft.Testing.Platform/OutputDevice/TerminalOutputDevice.cs	Replace session-lifetime-handler-based state with role-based state for end-of-run and artifact classification.
samples/Playground/Program.cs	Enable TRX provider in the sample by default.
samples/Playground/Playground.csproj	Add TRX report extension project reference needed by the sample.

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