.NET: [Breaking] Restructure agent skills to use multi-source architecture (#4871)
* initial commit
* address comments
* address comments
* address comments
* address comments
* rename executor to runner to align naming with python implementation
* rename runner execute method to run method
* remove poc leftovers and fix compilation issues
* make script runner optional
* remove unnecessary pragmas
* make resources and scripts props virtual
* address comments
* update comment for name validation regex
* address comments
SergeyMenshykh