Adding Azure monitor metrics to TSC repo for node availability

[shaheislamdfe]

Context

We need a way to alert when our nodepool is close to max capacity to preempty scaling if necessary.

Changes proposed in this pull request

Adding an Azure Monitor Metric Alert with an Action group for each environment and dynamically setting the threshold based on the max count.

Guidance to review

This has been checked in the Azure Monitor UI and is correctly working.

Checklist

• I have performed a self-review of my code, including formatting and typos
• I have cleaned the commit history
• I have added the Devops label
• I have attached the pull request to the trello card

[neillturner]

you should not create the action group in the makefile but in terraform. see my PR #343.
we probably need to co-ordinate these two PRs so we share the same action group and decide if it goes to email or slack or maybe both. Also i put my azure alert in the existing monitor tf file.

[RMcVelia]

you should not create the action group in the makefile but in terraform. see my PR #343. we probably need to co-ordinate these two PRs so we share the same action group and decide if it goes to email or slack or maybe both. Also i put my azure alert in the existing monitor tf file.

Our existing standard is to create all the action groups via the Makefile. We use email as slack webhooks for azure alerting require extra infrastructure (logic app or similar).

[neillturner]

as rick says we create action group in makefile this is approved