StackHCI Registration process Improvements (#18230)

* initial changes

* updated changelog

* change code to fix linter issues

* updated help files

* moved new parameter to the end to avoid being flagged as breaking changes

* moved another new parameter to the end

* adding back [ValidateNotNullOrEmpty()] to check if pipeline allows it

* remove ValidateNotNullOrEmpty() as it is considered as breaking change

* Update ChangeLog.md

Co-authored-by: Niranjan B <[email protected]>
Co-authored-by: Yabo Hu <[email protected]>

Author: 3 people