Automatically generated policies for all Metrics

[arjenhuitema]

Overview/Summary

This PR includes the first iteration of policy automation using YAML. Policies are designated as preview by default, except when they are duplicates of existing ALZ policies.

Right now, the scope is limited to Metric alerts, applicable to static as well as dynamic thresholds. Log and Activity come with extra dependencies and considerations to address, which will be included in the future.

The automation workflow will also be implemented at a later stage.

This PR fixes/adds/changes/removes

1. PowerShell script to automate Policy creation from YAML data.
2. Policy templates.
3. Initial preview Policy version for all Metrics.

As part of this Pull Request I have

• Read the Contribution Guide and ensured this PR is compliant with the guide
• Checked for duplicate Pull Requests
• Associated it with relevant GitHub Issues or ADO Work Items (Internal Only)
• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Ensured PR tests are passing
• Updated relevant and associated documentation (e.g. Contribution Guide, Docs etc.)