PerfDiff: Fix resource management and disposal patterns

[coderabbitai]

Description

Resource management issues identified where objects implementing IDisposable are not properly disposed.

Issues Identified from PR #565

Disposal Issues

• Program.cs:49: cancellationTokenSource not disposed when no longer needed
• Risk of resource leaks in command-line application

API Design Issues

• Multiple out parameter warnings in regression strategies
• While legitimate for returning detailed results, consider if alternative patterns might be cleaner

Affected Files

• src/tools/PerfDiff/Program.cs
• src/tools/PerfDiff/BDN/Regression/IBenchmarkRegressionStrategy.cs
• src/tools/PerfDiff/BDN/Regression/PercentageRegressionStrategy.cs
• src/tools/PerfDiff/BDN/Regression/PercentileRegressionStrategy.cs
• src/tools/PerfDiff/BDN/Regression/RegressionStrategyHelper.cs

Suggested Solutions

• Implement proper using statements or try-finally blocks for disposable resources
• Consider returning result objects instead of out parameters where appropriate
• Add resource management unit tests

Reference

• Original PR: feat: modularize PerfDiff regression detection, update analyzer reporting, and clarify CI performance documentation #565
• Static analysis: Codacy warnings