Update SyncTriggers to use /sync ARM API

[mathewc]

Once the ANT 82 deployment is complete, we should update to use the /host/default/sync ARM API. It already internally does the right thing w.r.t. v1/v2 version handling. Additionally, this centralizes the sync logic in one place, so we can control it better.

[mathewc]

Associated Portal work item: https://github.com/Azure/azure-functions-ux/issues/3872