Add Collection expressions to the language reference

[BillWagner]

Contributes to #36356

This PR has the tasks from the #36356 (comment)

Reorganize some of the content: Move the collections and arrays content from the programming guide to the language reference. Consolidate the articles on arrays into a single article. Then update the consolidated article by moving snippets and updating the samples.

Fix existing issues: Edit pass on collections article. Simplify examples and remove outdated examples. Update text. Instead of listing all collections, refer to articles in the .NET fundamentals and API reference where all collections are listed.

Fixes #20541: Don't list all collection types. That's brittle. Instead, refer to locations in the standard section, and the API reference where all collections can be found for the current version.

Edit pass on arrays article. Simplify and combine many of the samples. Update the related text. Update the samples and the text to match our current style.

Fixes #27181: Rewrite the text that describes the default value for any array elements.
Fixes #29181: Specify that 2 D arrays can be thought of as [row, column].

Add collection expressions article: This is the new article that covers collection expressions.

Internal previews for significant changes:

• Collections
• Arrays
• Collection expressions New article.

Other files changed are for updated links.

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Internal previews

Toggle expand/collapse

📄 File	🔗 Preview link
docs/csharp/advanced-topics/expression-trees/index.md	Expression Trees
docs/csharp/language-reference/builtin-types/arrays.md	docs/csharp/language-reference/builtin-types/arrays
docs/csharp/language-reference/builtin-types/collections.md	docs/csharp/language-reference/builtin-types/collections
docs/csharp/language-reference/operators/collection-expressions.md	docs/csharp/language-reference/operators/collection-expressions
docs/csharp/language-reference/operators/member-access-operators.md	Member access operators and expressions - the dot, indexer, and invocation operators.
docs/csharp/language-reference/operators/new-operator.md	"new operator - Create and initialize a new instance of a type"
docs/csharp/language-reference/statements/iteration-statements.md	Iteration statements - for, foreach, do, and while
docs/csharp/programming-guide/classes-and-structs/how-to-use-implicitly-typed-local-variables-and-arrays-in-a-query-expression.md	docs/csharp/programming-guide/classes-and-structs/how-to-use-implicitly-typed-local-variables-and-arrays-in-a-query-expression
docs/csharp/programming-guide/classes-and-structs/implicitly-typed-local-variables.md	Implicitly typed local variables (C# Programming Guide)
docs/csharp/programming-guide/concepts/index.md	"Programming Concepts (C#)"
docs/csharp/programming-guide/concepts/iterators.md	Iterators (C#)
docs/csharp/programming-guide/generics/generics-and-arrays.md	Generics and Arrays (C# Programming Guide)
docs/csharp/programming-guide/index.md	C# programming guide
docs/csharp/tour-of-csharp/features.md	docs/csharp/tour-of-csharp/features
docs/csharp/tour-of-csharp/index.md	A tour of the C# language
docs/csharp/whats-new/csharp-12.md	What's new in C# 12 - C# Guide
docs/fundamentals/code-analysis/quality-rules/ca1814.md	CA1814: Prefer jagged arrays over multidimensional
docs/standard/serialization/system-text-json/supported-collection-types.md	docs/standard/serialization/system-text-json/supported-collection-types

[gewarren]

One other thing - there's no default titleSuffix for the /csharp folder. Might make sense to add a default title suffix of "C#"?