Allow combining of -Skip and -SkipLast parameters in Select-Object cmdlet. (#18849)

* Added SkipLast parameter set to Skip parameter and updated tests

* Using Should -BeExactly with string

* Update test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1

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Co-authored-by: Travis Plunk <travis.plunk@microsoft.com>
Co-authored-by: Travis Plunk <github@ez13.net>

src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs

@@ -144,10 +144,11 @@ namespace Microsoft.PowerShell.Commands
         private bool _firstOrLastSpecified;
 
         /// <summary>
-        /// Skips the specified number of items from top when used with First, from end when used with Last.
+        /// Skips the specified number of items from top when used with First, from end when used with Last or SkipLast.
         /// </summary>
         /// <value></value>
         [Parameter(ParameterSetName = "DefaultParameter")]
+        [Parameter(ParameterSetName = "SkipLastParameter")]
         [ValidateRange(0, int.MaxValue)]
         public int Skip { get; set; }