Sync triggers should return a warning/error if no functions are found after deployment

A user has a .NET isolated function app, and the `host.json` file includes an entry for an extension bundle. After a deployment is performed, the host fails to enumerate and discover the app's functions, and no error or warning is shown to the user. If sync triggers fail to enumerate any functions after deployment, an error message or warning should be returned.

In this case, to fix the issue, the user must remove the extension bundle entry from the `host.json`. However, currently, no error or warning is shown to the user.

Start by tracing the deployment sync-triggers path for the .NET isolated function app and the host.json extension-bundle scenario described in the issue. Verify the behavior when no functions are enumerated after deployment, and consider the work complete when that condition returns a user-visible warning or error.

Written by the indexing model from the issue text.