Edit pass for LINQ "get started" section.

[BillWagner]

This PR moves the content for the section on "Get Started with LINQ" to match the TOC. It will be easiest to review commit-by-commit:

1. Fix existing issues with content that moves.
   • Fixes Missing directive #28863 - Add a note to include a using for System.Linq, unless your project includes implicit usings. Add links to both.
   • Fixes Wrong condition in Linq for Query #7 #36684 - The text in the article used the phrase "between 3 and 7", but the sample was less than 3 or greater than 7. Fix the code to match the text.
2. Move all moving content (articles, images, included snippets).
3. Refactor sample code and tests.
4. Edit article text.
5. Use clean-repo to fix links
6. Use clean-repo to replace absolute links with relative links
7. Remove redundant links.

As part of the major edits:

Fixes #28606
Fixes #36501

This table shows the change and preview before the final commits updating links. These contains contain the major changes:

---

Internal previews

📄 File	🔗 Preview link
docs/csharp/linq/get-started/features-that-support-linq.md	C# Features That Support LINQ
docs/csharp/linq/get-started/introduction-to-linq-queries.md	Introduction to LINQ Queries (C#)
docs/csharp/linq/get-started/query-expression-basics.md	Query expression basics (LINQ in C#)
docs/csharp/linq/get-started/type-relationships-in-linq-query-operations.md	Type Relationships in LINQ Query Operations (C#)
docs/csharp/linq/get-started/write-linq-queries.md	docs/csharp/linq/get-started/write-linq-queries
docs/csharp/linq/index.md	Language Integrated Query (LINQ)

---

Internal previews

Toggle expand/collapse

📄 File	🔗 Preview link
docs/csharp/language-reference/compiler-messages/cs1941.md	Compiler Error CS1941
docs/csharp/language-reference/compiler-messages/ref-modifiers-errors.md	Errors and warnings associated with reference parameters, variables, and returns
docs/csharp/language-reference/keywords/from-clause.md	"from clause - C# Reference"
docs/csharp/language-reference/keywords/select-clause.md	select clause (C# Reference)
docs/csharp/linq/get-started/features-that-support-linq.md	docs/csharp/linq/get-started/features-that-support-linq
docs/csharp/linq/get-started/introduction-to-linq-queries.md	Introduction to LINQ Queries (C#)
docs/csharp/linq/get-started/query-expression-basics.md	Query expression basics (LINQ in C#)
docs/csharp/linq/get-started/type-relationships-in-linq-query-operations.md	Type Relationships in LINQ Query Operations (C#)
docs/csharp/linq/get-started/write-linq-queries.md	docs/csharp/linq/get-started/write-linq-queries
docs/csharp/linq/handle-exceptions-in-query-expressions.md	Handle exceptions in query expressions
docs/csharp/linq/index.md	Language Integrated Query (LINQ) in C#
docs/csharp/misc/cs1949.md	Compiler Error CS1949
docs/csharp/programming-guide/concepts/linq/how-to-query-an-arraylist-with-linq.md	How to query an ArrayList with LINQ (C#)
docs/csharp/programming-guide/concepts/linq/walkthrough-writing-queries-linq.md	Walkthrough: Writing Queries in C# (LINQ)
docs/csharp/tutorials/working-with-linq.md	docs/csharp/tutorials/working-with-linq
docs/csharp/whats-new/csharp-version-history.md	The history of C#
docs/framework/data/adonet/ef/language-reference/queries-in-linq-to-entities.md	Queries in LINQ to Entities
docs/framework/data/adonet/queries-in-linq-to-dataset.md	"Queries in LINQ to DataSet"
docs/framework/data/adonet/sql/linq/aggregate-queries.md	Aggregate Queries
docs/framework/data/adonet/sql/linq/how-to-call-user-defined-functions-inline.md	How to: Call User-Defined Functions Inline
docs/framework/data/adonet/sql/linq/how-to-query-for-information.md	"How to: Query for Information"
docs/framework/data/adonet/sql/linq/linq-to-sql-queries.md	LINQ to SQL Queries
docs/framework/data/adonet/sql/linq/query-concepts.md	docs/framework/data/adonet/sql/linq/query-concepts
docs/framework/data/adonet/sql/linq/walkthrough-simple-object-model-and-query-csharp.md	Walkthrough: Simple Object Model and Query (C#)
docs/framework/data/adonet/sql/linq/walkthrough-simple-object-model-and-query-visual-basic.md	"Walkthrough: Simple Object Model and Query (Visual Basic)"
docs/fundamentals/apicompat/assembly-validation.md	Assembly validation
docs/standard/collections/index.md	Collections and Data Structures
docs/standard/linq/concepts-terminology-functional-transformation.md	docs/standard/linq/concepts-terminology-functional-transformation
docs/standard/linq/generate-text-files-xml.md	How to generate text files from XML (LINQ to XML)
docs/standard/linq/query-xml-trees-overview.md	Query XML trees overview - LINQ to XML

[tdykstra]

LGTM, just noted a few nits.