Clarify that positional parameters can create fields

[BillWagner]

Record types with positional parameters can synthesize fields as well as parameters. Make that more clear.

Fixes #44041

The only significant changes are in records.md. The other files are only updating an anchor.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/fundamentals/coding-style/identifier-names.md	C# identifier naming rules and conventions
docs/csharp/fundamentals/functional/deconstruct.md	Deconstructing tuples and other types
docs/csharp/fundamentals/types/records.md	Introduction to record types in C#
docs/csharp/language-reference/attributes/general.md	docs/csharp/language-reference/attributes/general
docs/csharp/language-reference/builtin-types/record.md	Records (C# reference)
docs/csharp/language-reference/keywords/required.md	"required modifier"
docs/csharp/language-reference/operators/deconstruction.md	Deconstruction expression - Extract properties of fields from a tuple or other user-defined type
docs/csharp/language-reference/operators/patterns.md	Pattern matching - the is and switch expressions, and operators and, or, and not in patterns
docs/standard/serialization/system-text-json/immutability.md	docs/standard/serialization/system-text-json/immutability