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/powershell/engine/Module/ModulePath.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 Describe "SxS Module Path Basic Tests" -tags "CI" {
 
     BeforeAll {
@@ -39,7 +41,6 @@ Describe "SxS Module Path Basic Tests" -tags "CI" {
         $env:PSModulePath = $originalModulePath
     }
 
-
     It "validate sxs module path" {
 
         $env:PSModulePath = ""
@@ -53,7 +54,6 @@ Describe "SxS Module Path Basic Tests" -tags "CI" {
         $paths[2].TrimEnd([System.IO.Path]::DirectorySeparatorChar) | Should Be $expectedSystemPath
     }
 
-
     It "ignore pshome module path derived from a different powershell core instance" -Skip:(!$IsCoreCLR) {
 
         ## Create 'powershell' and 'pwsh.deps.json' in the fake PSHome folder,