[resource/monitoring_alert_policy] Add support and docs example for MQL Alerting Policy

[naseemkullah]

Description

https://cloud.google.com/monitoring/mql/alerts have recently been made available, they can be created in the UI, but have not had luck with terraform

New or Affected Resource(s)

• google_monitoring_alert_policy

References

https://cloud.google.com/monitoring/mql/alerts

[femnad]

Added a PR proposing to address this issue.

[yegle]

It looks like hashicorp/terraform-provider-google-beta#2651 just missed the v3.45.0 cutoff.

What's the release cadence for the beta provider? Thank you!

[nat-henderson]

It should be released next Monday. :)