Replace custom TestMethodForPlatformAttribute with MSTest OSCondition

[Copilot]

MSTest 4.0+ provides OSCondition attribute for platform-specific tests, making the custom TestMethodForPlatformAttribute obsolete (MSTEST0061).

Changes

• Replaced custom attribute usage across 6 test files (14 test methods total):

  // Before
  [TestMethodForPlatform(nameof(OSPlatform.Windows))]
  public void TestMethod() { }
  
  // After
  [TestMethod]
  [OSCondition(OperatingSystems.Windows)]
  public void TestMethod() { }

• Removed test/Renci.SshNet.Tests/Common/TestMethodForPlatformAttribute.cs

• Cleaned up unused imports: System.Runtime.InteropServices and Renci.SshNet.Tests.Common

Affected Test Classes

• ForwardedPortDynamicTest_*_PortStarted_ChannelNotBound (2 files)
• *ConnectorTest_Connect_TimeoutConnectingToProxy (4 files: Direct, Http, Socks4, Socks5)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>TestMethodForPlatformAttribute can be replaced with [OSCondition(OperatingSystems.Windows)]</issue_title>
<issue_description>According to https://learn.microsoft.com/dotnet/core/testing/mstest-analyzers/mstest0061 the

SSH.NET/test/Renci.SshNet.Tests/Common/TestMethodForPlatformAttribute.cs

Line 11 in 89ea230

public sealed class TestMethodForPlatformAttribute : TestMethodAttribute

can be replaced with e.g.:

[TestMethod]
[OSCondition(OperatingSystems.Windows)]

</issue_description>

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

• Fixes TestMethodForPlatformAttribute can be replaced with [OSCondition(OperatingSystems.Windows)] #1763

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[drieseng]

Thx!