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/Language/Scripting/NativeExecution/NativeCommandArguments.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 Describe "Native Command Arguments" -tags "CI" {
     # When passing arguments to native commands, quoted segments that contain
     # spaces need to be quoted with '"' characters when they are passed to the

test/powershell/Language/Scripting/NativeExecution/NativeCommandProcessor.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 Describe 'Native pipeline should have proper encoding' -tags 'CI' {
     It '$OutputEncoding should be set to UTF8 without BOM' {
         $OutputEncoding.BodyName | Should Be "utf-8"

test/powershell/Language/Scripting/NativeExecution/NativeLinuxCommands.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 Describe "NativeLinuxCommands" -tags "CI" {
     BeforeAll {
         $originalDefaultParams = $PSDefaultParameterValues.Clone()

test/powershell/Language/Scripting/NativeExecution/NativeStreams.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 Describe "Native streams behavior with PowerShell" -Tags 'CI' {
     $powershell = Join-Path -Path $PsHome -ChildPath "pwsh"
 

test/powershell/Language/Scripting/NativeExecution/NativeUnixGlobbing.Tests.ps1

@@ -1,3 +1,5 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
 
 Describe 'Native UNIX globbing tests' -tags "CI" {