Add AssertInRange, AssertNotNullOrWhiteSpace, and CheckNotNullOrEmpty to ArgumentDefinition

[Copilot]

• Add BuildAssertNotNullOrWhiteSpace method to ArgumentDefinition.cs
• Add BuildAssertInRange method to ArgumentDefinition.cs
• Add BuildCheckNotNullOrEmpty method to ArgumentDefinition.cs
• Update BuildMethods() to include the 3 new methods
• Update generated TestProjects/Local/Sample-TypeSpec/src/Generated/Internal/Argument.cs
• Update docs/samples/client/csharp/SampleService/SampleClient/src/Generated/Internal/Argument.cs
• Add tests to ArgumentTests.cs (10 new tests, all passing)
• Remove ThrowArgumentOutOfRangeException helper — inline Throw directly in BuildAssertInRange
• Build and verify tests pass (17 ArgumentTests pass)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add Additional Argument Internal Helper Methods</issue_title>
<issue_description>The .net autorest generator supported generated these internal helper methods, which are consumed by the .NET storage library:

• AssertInRange
• AssertNotNullOrWhitespace
• CheckNotNullOrEmpty

We should update our generator to support generating these internal helper methods.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add Additional Argument Internal Helper Methods #9793

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commit: fe338cd

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