Improve ValidateLength error message consistency and refactor validation tests (PowerShell#25806)

Author: jorgeasaurus

src/System.Management.Automation/resources/Metadata.resx

@@ -175,7 +175,7 @@
     <value>The character length ({1}) of the argument is too short. Specify an argument with a length that is greater than or equal to "{0}", and then try the command again.</value>
   </data>
   <data name="ValidateLengthMaxLengthFailure" xml:space="preserve">
-    <value>The character length of the {1} argument is too long. Shorten the character length of the argument so it is fewer than or equal to "{0}" characters, and then try the command again.</value>
+    <value>The character length ({1}) of the argument is too long. Specify an argument with a length that is shorter than or equal to "{0}", and then try the command again.</value>
   </data>
   <data name="ValidateSetFailure" xml:space="preserve">
     <value>The argument "{0}" does not belong to the set "{1}" specified by the ValidateSet attribute. Supply an argument that is in the set and then try the command again.</value>