Fix changing directory times

[GerardSmit]

This PR fixes the following methods when the path is a directory:

• SetCreationTime
• SetLastAccessTime
• SetLastWriteTime

The current implementation uses File, which is invalid for directories. When you try to invoke the method with a directory path, you'll get the following exception (.NET 8 and .NET FX 4.8):

System.UnauthorizedAccessException
Access to the path 'C:\Sources\zio\src\Zio.Tests\bin\Debug\net472\TestCreateDirectory' is denied.

The XML documentation is not clear whether this should be supported or not. In the summary it says changing the file time:

zio/src/Zio/IFileSystem.cs

Lines 131 to 133 in ae0b1ca

	/// <summary>
	/// Sets the date and time the file was created.
	/// </summary>

But in the path-param it's saying it accepts files and directories:

zio/src/Zio/IFileSystem.cs

Line 134 in ae0b1ca

/// <param name="path">The path to a file or directory for which to set the creation date and time.</param>

If we decide to merge this PR, should we change the XML documentation summary, so it mentions directories as well?