Add CI/CD to .NET project (Azure#47964)

* Add tests

* Record unit tests

* Add mock credential to avoid authentication issues in the playback

* Add licenseheader

Author: nick863

sdk/ai/Azure.AI.Projects/assets.json

@@ -1,6 +1,6 @@
 {
   "AssetsRepo": "Azure/azure-sdk-assets",
   "AssetsRepoPrefixPath": "net",
-  "TagPrefix": "net/openai/Azure.AI.OpenAI.Assistants",
-  "Tag": "net/openai/Azure.AI.OpenAI.Assistants_11106f4f8f"
+  "TagPrefix": "net/ai/Azure.AI.Projects",
+  "Tag": "net/ai/Azure.AI.Projects_dc2b082d80"
 }