add handling for vmss scaling events to improve accuracy

[JaydenLiang]

internal issue id: 0739446

background:
When a vm has been deleted, the corsesponding autoscale record still remains in the DB. The record should be ideally deleted.
And there's API cache to reduce the ARM API call consumption, if a vm no longer exists, such cache should be ideally deleted.

solution:
create Azure VMSS alerts rules that is triggered by vmss activity logs and sends events to the Autoscale handler Azure function.
add handling in the function for each of such events (can be developed one by one).

initially, the first event to be handled should be action Microsoft.Compute/virtualMachineScaleSets/delete/action