## Motivation
I have a PR where there are many new xUnit tests.
It would also be useful to create new xUnit tests for public APIs.
The number of xUnit tests will increase and their ordering is required.
## PR Summary
- Move C# xUnit tests in new folder. This allows to put new xUnit tests in directory structure in accordance with directory structure where cs files are.
- Use an xUnit TestCaseOrderer attribute to sequentially process tests for `powershell.config.json`.
- Update README.md
- A race condition was fixed which allowed to run all XUnit tests in single batch job.
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
