Clean up [SymmetricAlgorithm].Create samples

[bartonjs]

Summary

Updates the code in the [SymmetricAlgorithm].Create samples.

• Removes the samples from the Create(string) overload
  • The method is being marked as Obsolete in .NET 7
  • It had a different sample than Create() for C#, but reused the Create() sample in VB and C++/CLI
• Fixes the bug in the sample that assumed CryptoStream.Read aggressively fills the destination.
• Adds using statements (or the language-specific equivalent) for all IDisposable values.
• Uses names for parameters and locals that are consistent with .NET guidelines and best practices.
• Changes C++/CLI to use function prototypes so the functions are presented in the same order across all three languages.
• Changes the method declarations in VB to a more canonical style.

Contributes to #8140. (Will update to "Fixes" after doing 3DES and RC2, once DES gets vetted first)

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Issue Details

---

Summary

Updates the code in the [SymmetricAlgorithm].Create samples.

• Removes the samples from the Create(string) overload
  • The method is being marked as Obsolete in .NET 7
  • It had a different sample than Create() for C#, but reused the Create() sample in VB and C++/CLI
• Fixes the bug in the sample that assumed CryptoStream.Read aggressively fills the destination.
• Adds using statements (or the language-specific equivalent) for all IDisposable values.
• Uses names for parameters and locals that are consistent with .NET guidelines and best practices.
• Changes C++/CLI to use function prototypes so the functions are presented in the same order across all three languages.
• Changes the method declarations in VB to a more canonical style.

Contributes to #8140. (Will update to "Fixes" after doing 3DES and RC2, once DES gets vetted first)

Author:	bartonjs
Assignees:	bartonjs
Labels:	area-System.Security
Milestone:	-

[opbld31]

Docs Build status updates of commit 7af69c7:

✅ Validation status: passed

File	Status	Preview URL	Details
snippets/cpp/VS_Snippets_CLR/Cryptography.DES.Create.File/CPP/fileexample.cpp	✅Succeeded	View
snippets/cpp/VS_Snippets_CLR/Cryptography.DES.Create.Memory/CPP/memoryexample.cpp	✅Succeeded	View
snippets/csharp/System.Security.Cryptography/DES/Create/fileexample.cs	✅Succeeded	View
snippets/csharp/System.Security.Cryptography/DES/Create/fileexample1.cs	✅Succeeded
snippets/csharp/System.Security.Cryptography/DES/Create/memoryexample.cs	✅Succeeded	View
snippets/csharp/System.Security.Cryptography/DES/Create/memoryexample1.cs	✅Succeeded
snippets/csharp/System.Security.Cryptography/DES/Create/project.csproj	✅Succeeded
snippets/visualbasic/VS_Snippets_CLR/Cryptography.DES.Create.File/VB/fileexample.vb	✅Succeeded	View
snippets/visualbasic/VS_Snippets_CLR/Cryptography.DES.Create.File/VB/project.csproj	✅Succeeded
snippets/visualbasic/VS_Snippets_CLR/Cryptography.DES.Create.Memory/project.csproj	✅Succeeded
snippets/visualbasic/VS_Snippets_CLR/Cryptography.DES.Create.Memory/VB/memoryexample.vb	✅Succeeded	View
xml/System.Security.Cryptography/DES.xml	✅Succeeded	View

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