Refactor integraton tests for dotnet test

[mariam-abdulla]

This pull request includes several changes aimed at improving file handling, updating project configurations, and enhancing test utilities. The most important changes include the addition of new utility methods, renaming and refactoring classes, and updating project files to use a dynamic target framework.

File Handling Improvements:

• Added FindFileInParentDirectories method in PathUtility.cs to locate files in parent directories.

Code Refactoring:

• Renamed msbuildExitCode to msBuildExitCode for consistency in MSBuildHandler.cs.
• Renamed parameter projectFilePath to filePath in BuildOrRestoreProjectOrSolution method in MSBuildHandler.cs.

Test Utilities Enhancements:

• Added ReadMSTestVersionFromProps and UpdateProjectFileWithMSTestVersion methods in TestAsset.cs to handle MSTest version updates.
• Introduced DotnetVersionHelper and RegexPatternHelper classes in Utilities to assist with version management and regex pattern generation. [1] [2]

Project Configuration Updates:

• Updated various .csproj files to use $(CurrentTargetFramework) instead of hardcoded target frameworks. [1] [2] [3] [4] [5]
• Removed global.json file from the MultiTestProjectSolutionWithDiscoveredTests directory.

Class Renaming:

• Renamed Constants to TestingConstants in TestingConstants.cs to better reflect its purpose.

Relates to #45927