Tutorial: Choosing between tuples, records, structs, and classes

[BillWagner]

Fixes #51996

This pull request introduces a new tutorial to the C# Fundamentals documentation that helps developers choose between tuples, records, structs, classes, and interfaces by walking through a practical coffee shop example. It includes a comprehensive, example-driven guide, a complete code sample, and updates the table of contents to surface the new material.

New tutorial and code sample:

• Added a detailed tutorial, choosing-types.md, that explains when to use tuples, record classes, record structs, classes, and interfaces, with practical examples and a decision guide table.
• Introduced a full runnable code sample in snippets/choosing-types/Program.cs that demonstrates each type in context, including tuples, records, structs, classes, and interfaces.

Documentation navigation:

• Updated the table of contents (toc.yml) to add the new tutorial under the Fundamentals section for easier discovery.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/fundamentals/tutorials/choosing-types.md	Tutorial: Choose between tuples, records, structs, and classes
docs/csharp/toc.yml	Taken from https://github.com/dotnet/roslyn/wiki/Samples-and-Walkthroughs

[Copilot]

Pull request overview

Adds a new C# Fundamentals tutorial that helps learners choose between tuples, record classes, record structs, classes, and interfaces using a coffee shop–based walkthrough, and surfaces the tutorial in the C# table of contents.

Changes:

• Added a new tutorial page (choosing-types.md) with scenario-driven guidance and a quick decision table.
• Added a runnable sample (snippets/choosing-types/Program.cs) that demonstrates tuples, records, structs, classes, inheritance, and interfaces.
• Updated docs/csharp/toc.yml to include the new tutorial under Fundamentals tutorials.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
docs/csharp/toc.yml	Adds a TOC entry so the new tutorial is discoverable under Fundamentals tutorials.
docs/csharp/fundamentals/tutorials/choosing-types.md	Introduces the new tutorial content and references snippet regions for examples.
docs/csharp/fundamentals/tutorials/snippets/choosing-types/Program.cs	Provides the example code regions used throughout the tutorial.