az monitor autoscale rule create bugs and missing config fields

### Overview
3 Issues Discovered.

1. **Autoscale direction when using 'to'**

https://github.com/Azure/azure-cli/blob/1fec5c4e721d2313e91c15a5ba542025759131d6/src/azure-cli/azure/cli/command_modules/monitor/util.py#L53

When you use --scale to X in az monitor autoscale rule create it sets the direction to None. This breaks the autoscale rule.

FYI - when creating the same 'to X' rule in the portal this populates the direction correctly with either an 'Increase' or 'Decrease' depending on the other rules in the profile.


2. **dividePerInstance option and parameter is missing**
Additionally, the dividePerInstance field is missing from the autoscale rule cli template as seen here and is a critical missing component (it just seems to get defaulted to true at the moment which breaks my scaling rule needs!). This is populated and available when creating a rule in the portal:


https://github.com/Azure/azure-cli/blob/1fec5c4e721d2313e91c15a5ba542025759131d6/src/azure-cli/azure/cli/command_modules/monitor/operations/autoscale-parameters-template.json#L15

**These are both broken/missing features.**

[Referencing this previous issue:]
#https://github.com/Azure/azure-cli/issues/16027#issue-749669485

**_EDIT_** Found another issue
3. 'az monitor autoscale create' is not idempotent and will wipe all the existing profiles and rules if run again. This kind of makes it a bit useless to be honest as it would wipe profiles and other rules for the autoscale setting in other deployments each time. A check for if it already exists needs to be implemented to make it more in line with the other az commands and patterns.