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
* corrected use of PSModulePath casing to be consistent with Windows PowerShell
addresses #3227
* addressing review feedback
make "PSModulePath" into const
fixed some test workarounds due to failures for external reasons that wasn't meant to be checked in
* addressing review feedback
make "PSModulePath" into const
fixed some test workarounds due to failures for external reasons that wasn't meant to be checked in