Change test duration to TimeSpan

[Malcolmnixon]

This PR:

• changes the test duration to a TimeSpan
• adds support for all TRX outcome types

New tests have been added which deserialize standard TRX test files and confirm the contents.

[Copilot]

Pull Request Overview

This PR changes the test duration property from a double (seconds) to a TimeSpan type and adds comprehensive support for all TRX test outcome types. The changes include refactoring the TestOutcome enum to include all standard TRX outcomes with extension methods for classification, and adding thorough test coverage with real TRX file examples.

• Changes test duration from double to TimeSpan for better type safety and clarity
• Expands TestOutcome enum to support all TRX outcome types with helper extension methods
• Adds comprehensive test coverage using real TRX example files

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/DemaConsulting.TestResults/TestResult.cs	Changes Duration property from double to TimeSpan and default outcome from Skipped to NotExecuted
src/DemaConsulting.TestResults/TestOutcome.cs	Expands enum with all TRX outcomes and adds extension methods for outcome classification
src/DemaConsulting.TestResults/IO/TrxSerializer.cs	Updates serialization/deserialization to handle TimeSpan duration and improved error handling
test/DemaConsulting.TestResults.Tests/TestOutcomeTests.cs	New test file for comprehensive testing of TestOutcome extension methods
test/DemaConsulting.TestResults.Tests/IO/TrxExampleTests.cs	New test file validating deserialization against real TRX files
test/DemaConsulting.TestResults.Tests/IO/TrxSerializerTests.cs	Updates existing tests to use TimeSpan for duration