Support .slnf file format in dotnet test

[mariam-abdulla]

This pull request focuses on refactoring and improving the handling of solution and project files in the CLI, as well as enhancing the build process. The most important changes include the introduction of new methods for parsing solution filter files, simplifying the MSBuildHandler class, and updating constants to support solution filter files.

Refactoring and Enhancements:

• src/Cli/dotnet/SlnFileFactory.cs: Introduced new methods GetSolutionPathFromFilteredSolutionFile and ParseSolutionFilterFile to handle solution filter files, and refactored CreateFromFilteredSolutionFile to use these methods. [1] [2] [3] [4]

Simplification of MSBuildHandler:

• src/Cli/dotnet/commands/dotnet-test/MSBuildHandler.cs: Removed redundant methods and simplified the build process by delegating solution and project handling to MSBuildUtility. Also, removed the degree of parallelism parameter and the validation of build path options. [1] [2] [3] [4] [5]

Support for Solution Filter Files:

• src/Cli/dotnet/commands/dotnet-test/CliConstants.cs: Added support for .slnf files by updating the SolutionExtensions array and introducing SolutionFilterExtensionPattern.
• Solution filter files are now supported using --solution, e.g. dotnet test --solution "TestProjects.slnf".
• If we run dotnet test and there exists only one .slnf file in the directory, we will run projects inside this .slnf file. But if we have multiple .slnf files, we will throw an error to specify the solution file. If we have 1 solution file (.sln/.slnx) and multiple .slnf files, we run only the solution file.

Relates to #45927

[edvilme]

Excited to see this getting support! :)

[edvilme]

I know it is just a few lines, and just tossing some thoughts around, but maybe we could create a helper method that parses the .slnf into a valid JsonElement and have GetSolutionPathFromFilteredSolutionFile and CreateFromFilteredSolutionFile call it?
If possible I would advocate to avoiding reading and parsing the file more than once

[kasperk81]

Suggested change

	using JsonDocument jsonDocument = JsonDocument.Parse(File.ReadAllText(filteredSolutionPath));
	JsonElement jsonElement = jsonDocument.RootElement;
	JsonElement filteredSolutionJsonElement = jsonElement.GetProperty("solution");
	string originalSolutionPath = filteredSolutionJsonElement.GetProperty("path").GetString();
	return originalSolutionPath;
	JsonNode? jsonNode = JsonNode.Parse(File.ReadAllText(filteredSolutionPath));
	string? originalSolutionPath = jsonNode?["solution"]?["path"]?.GetValue<string>();
	return originalSolutionPath!;

[kasperk81]

using System.Text.Json.Nodes;

[mariam-abdulla]

It's advised to use JsonNode for scenarios where we need to create or modify JSON data and this is not the case.

[kasperk81]

JsonNode is high performance api for both reading and writing. it's much better than reading a full document just to access selective field, which is this case. plus it has succinct syntax to access props.

[edvilme]

Maybe

Suggested change

	private static JsonElement ParseSolutionFilterFile(string solutionFilterFilePath)
	private static JsonElement ParseSolutionFilterFileJson(string solutionFilterFilePath)

just to make it super clear that it returns a json?