Document projection initializers (simplified names) for anonymous types

[Copilot]

Added comprehensive documentation for anonymous type projection initializers, which allows developers to use simplified syntax when creating anonymous types. This feature lets you use local variables directly without explicitly specifying member names.

Changes Made

Documentation Enhancement

• Added a new "Projection initializers" section to the anonymous types documentation
• Provided clear explanations of when member names are inferred vs. when they must be explicit
• Added guidance on limitations and edge cases

Code Examples

Added practical examples demonstrating the simplified syntax:

// Explicit member names
var personExplicit = new { FirstName = "Kyle", LastName = "Mit" };

// Projection initializers (inferred member names)
var firstName = "Kyle";
var lastName = "Mit";
var personInferred = new { firstName, lastName };

The documentation now clearly shows that these two approaches create equivalent anonymous types, addressing the original request for side-by-side comparisons.

Additional Context

• Explains when member name inference fails (duplicate names, reserved names, invalid identifiers)
• References the existing IDE0037 style rule for enforcing consistent usage
• Uses terminology consistent with tuple projection initializers documentation

All code examples have been tested and verified to compile and run correctly. The documentation follows Microsoft Writing Style Guide conventions and includes proper cross-references.

Fixes #33322.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/fundamentals/types/anonymous-types.md	docs/csharp/fundamentals/types/anonymous-types

[BillWagner]

This is a great start. One sentence is too vague.

[BillWagner]

This is now ready for final review.

[gewarren]

Please add periods in code comments.

[BillWagner]

Please add periods in code comments.

@copilot Please make this change.

[Copilot]

Please add periods in code comments.

@copilot Please make this change.

Added periods to all code comments in the anonymous types examples as requested. (535b15b)