Update copyright and license headers (#6134)

Based on standard practices, we need to have a copyright and license notice at the top of each source file. Removed existing copyrights and updated/added copyright notices for .h, .cpp, .cs, .ps1, and .psm1 files.

Updated module manifests for consistency to have Author = "PowerShell" and Company = "Microsoft Corporation". Removed multiple line breaks.

Separate PR coming to update contribution document for new source files: #6140

Manually reviewed each change.

Fix #6073

test/PSReadLine/Program.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Management.Automation;
@@ -43,7 +43,6 @@ namespace TestPSReadLine
             PSConsoleReadLine.SetKeyHandler(new[] {"F2"}, PSConsoleReadLine.ValidateAndAcceptLine, "", "");
             PSConsoleReadLine.SetKeyHandler(new[] {"Enter"}, PSConsoleReadLine.AcceptLine, "", "");
 
-
             EngineIntrinsics executionContext;
             using (var ps = PowerShell.Create(RunspaceMode.CurrentRunspace))
             {